In-exsufflator Cough Assist Device in Patients With Symptomatic Bronchiectasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for In-exsufflator Cough Assist Device in Patients With Symptomatic Bronchiectasis (NCT00452114), a randomized na study. The primary outcome is Number of Suppurative Exacerbations Per Patient Per Year.

2. Clinical Question

3. Trial Design

The registry describes a randomized, controlled, parallel-group study with no masking. The two device groups were the in-exsufflator cough-assist group and the active-comparator flutter-valve group. The record identifies the sponsor as the University of Massachusetts, Worcester, and lists bronchiectasis as the condition.

The study began in 2004-04, and primary completion is listed as 2008-05. Its current registry status is terminated. The record lists enrollment as 28, but the posted primary-outcome summaries give group sizes of 12 for the in-exsufflator group and 10 for the flutter-device group. The registry record does not explain how those figures relate to each other, or provide a flow of participants from enrollment through analysis.

The treatment descriptions specify daily use of each device. The in-exsufflator applies positive and negative inspiratory pressure in a cycle intended to augment expiratory flow and cough force. The flutter valve delivers a low-pressure vibratory pulse during expiration. These descriptions establish what the devices were, but the registry record does not report details such as adherence, training, or other care received during the study.

The primary outcome was the number of suppurative exacerbations per patient during a 12-month period. The listed secondary outcomes were the St. George's Respiratory Questionnaire and the Cough-Specific Quality of Life Questionnaire, each assessed at 12 months. Although the study summary mentions costs and pulmonary function among its intended areas of interest, posted results for those measures are not reported in the registry record. The record also does not report the original design assumptions or a detailed statistical analysis plan.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Suppurative Exacerbations Per Patient Per Year, measured over 12 months.

The primary endpoint is the mean number of suppurative exacerbations per patient within a 12-month period. It is an event-rate outcome: it summarizes recurrent events in relation to the stated observation period, rather than simply indicating whether a participant experienced any exacerbation. The registry reports a mean and standard deviation for each group.

Counting exacerbations can describe the frequency of episodes over the follow-up period and is directly connected to the study's stated question about acute exacerbations. The interpretation depends on how events were defined, identified, and counted. The registry describes the endpoint as suppurative exacerbations but does not provide a fuller operational definition, such as how an episode was distinguished from another episode or how events were ascertained.

As general statistical context, event-rate outcomes can be useful when participants may experience repeated events. A comparison of rates condenses the difference in event frequency into a relative measure, while the group means retain the event counts per patient in their original form. Both forms can help readers understand a result, but neither by itself describes the circumstances or clinical importance of each event. The registry record does not report a threshold for a clinically important difference or a separate outcome for the time to a first exacerbation.

7. Results Posted in the Registry

• Participants in the Intervention Group (Cough In-exsufflator): 2.50 versus 2.30 (Number of events per patient) on control; rate ratio 1.09 (95% CI 0.63–1.87, approximate, Poisson model); p ≈ 0.764.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Quality of Life (St. George's Respiratory Questionnaire)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Participants in the Intervention Group (Cough In-exsufflator): mean 30.00 versus 24.00 on control; difference 6.00 (95% CI -3.69 to 15.69), standardized effect d = 0.50; z-test p = 0.225.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Participants in the Intervention Group (Cough In-exsufflator) and the control. The interval gives the range of effects that remain compatible with the data.

Quality of Life (Cough-Specific Quality of Life Questionnaire)

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Participants in the Intervention Group (Cough In-exsufflator): mean 48.00 versus 43.00 on control; difference 5.00 (95% CI -5.51 to 15.51), standardized effect d = 0.38; z-test p = 0.351.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Participants in the Intervention Group (Cough In-exsufflator) and the control. The interval gives the range of effects that remain compatible with the data.

The two posted quality-of-life outcomes have a broadly similar descriptive pattern: the mean scores are numerically higher in the in-exsufflator group than in the flutter-device group. Their mean-difference intervals each extend across zero, so the summaries do not establish a clear difference. The registry record does not describe whether higher values represent better or worse quality of life on either scale, and it supplies no threshold for a meaningful score change.

These outcomes relate to the primary result by addressing a different proposed consequence of airway clearance. The primary endpoint counts suppurative exacerbations, whereas the questionnaires measure reported quality of life. A pattern in questionnaire scores cannot establish a change in exacerbation frequency, and the primary event-rate estimate cannot by itself establish a quality-of-life difference. Taken together, the posted summaries do not provide a precise, consistent basis for a broader conclusion across these distinct outcomes.

The registry lists the secondary comparisons without reported analyses, and their p-values are unadjusted. When several outcomes are examined, chance alone can produce apparently notable differences. Without a stated multiplicity plan, the secondary findings carry less inferential weight than a result supported by a prespecified analysis that accounts for the number of comparisons. This is a general statistical concern, not a claim that any particular finding arose by chance.

The record does not report missing-data handling, analysis populations, or whether the questionnaire assessments were completed by all participants expected at 12 months. It also does not report scale interpretation details or adjusted analyses. These omissions limit what can be inferred from the secondary outcomes. Their most appropriate role is descriptive and exploratory: they add context about the outcomes recorded, but do not independently confirm or overturn the primary result.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Quality of Life (St. George's Respiratory Questionnaire)
• Quality of Life (Cough-Specific Quality of Life Questionnaire)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary endpoint is a count of repeated exacerbation events over a fixed observation period. The registry summarizes the outcome with a mean and standard deviation in each group, then gives a rate ratio comparing the in-exsufflator group with the flutter-device group. This makes it possible to read both the absolute group summaries and a relative contrast. The rate ratio is 1.087, and the posted p-value is 0.764.

What does a rate ratio express?

As general statistical explanation, a rate ratio compares event rates between groups. A value of 1 means the estimated rates are equal; a value above 1 means the numerator group's estimated rate is higher; and a value below 1 means it is lower. The comparison is relative, so it should be read alongside the group means and the observation period. Here, the rate ratio compares the in-exsufflator group against the flutter-device group for the 12-month outcome.

For outcomes with repeated events, participants can contribute more than one event. A rate analysis accounts for event frequency rather than reducing the outcome to whether any event occurred. The registry record does not provide participant-level event histories or explain how events were operationally separated and verified, so readers cannot inspect the distribution of counts or independently assess event ascertainment.

Why does over-dispersion matter?

As general statistical explanation, a simple Poisson model assumes that event-count variation follows a particular relationship to the mean. Over-dispersion occurs when variation is greater than that model expects. If it is present and not addressed, uncertainty can be understated and a comparison may appear more precise than it is. The registry reports standard deviations of 1.7 and 2.1 alongside means of 2.5 and 2.3, but it does not report a diagnostic for over-dispersion, a model specification, or an adjustment for it. The posted rate-ratio calculation is identified as Poisson-based; the registry record does not give a sponsor-reported model or analysis narrative.

The comparison statistics should be treated as unadjusted calculations from posted summary statistics. The registry record lists no reported analyses. It does not describe covariate adjustment, handling of recurrent events beyond the rate comparison, or whether the analysis followed an intention-to-treat or per-protocol approach. The participant population included in the outcome analysis is therefore not characterized beyond the group sizes in the result summaries.

What does the p-value say?

As general statistical explanation, a p-value describes how compatible the observed data are with a specified null model, under the assumptions used to calculate it. It is not the probability that the null hypothesis is true, nor does it indicate the probability that the result will be replicated. The posted unadjusted p-value of 0.764 does not provide evidence of a clear difference under conventional significance testing, but it cannot show that the groups are equivalent. A nonsignificant result can occur when the estimated difference is small, when data are variable, or when precision is limited.

A p-value also does not measure clinical importance. To assess importance, readers would need a justified threshold for a meaningful change and context about the consequences of exacerbations. Neither a threshold nor a detailed clinical interpretation is reported in the registry record. The confidence interval is more informative about the range of effects that remain compatible with the data, although it too depends on the analysis assumptions.

How should the questionnaire outcomes be understood?

The registry reports group means and standard deviations for two quality-of-life scales at 12 months, with unadjusted mean differences and confidence intervals. As general statistical explanation, a mean difference is the intervention-group mean minus the comparator-group mean. A confidence interval describes uncertainty around that estimated difference under the calculation's assumptions. For both posted questionnaire comparisons, the intervals include zero. The registry record does not state how favorable values are oriented on either scale, nor does it report a minimally important difference or a sponsor-reported analysis.

Multiple outcomes raise the possibility of chance findings when many comparisons are considered. As general statistical explanation, multiplicity refers to the increased chance of at least one apparently noteworthy result when several hypotheses are tested. The record includes a primary endpoint and two secondary quality-of-life outcomes, but does not report a multiplicity strategy. The secondary p-values are unadjusted, so they should be treated as exploratory rather than as independent confirmation of the primary result.

The listed analysis summaries are not a substitute for a complete statistical analysis plan. The registry record does not report the original sample-size justification, missing-data methods, interim analyses, model checks, or prespecified subgroup analyses. Those details matter because they determine how estimates and uncertainty should be interpreted. In their absence, the clearest reading is descriptive: consider the reported group summaries, the unadjusted contrasts, and the width of their intervals without attributing unreported analytical choices to the investigators.

11. Confidence Intervals and Precision

The primary rate-ratio estimate is 1.087. Its reported confidence interval extends from below 1 to 1.871. Because 1 represents equal rates, the interval includes the possibility of a lower rate in the in-exsufflator group as well as a higher rate. It therefore does not isolate a single direction or a narrow range of plausible relative effects. The exact lower endpoint is not repeated because the registry value has more than three decimal places.

A confidence interval is, in general, a range of values generated by a statistical procedure that reflects sampling uncertainty under the model and assumptions used. It is not a guarantee that the true effect lies in that particular interval, and it does not account for every possible source of error, such as incomplete outcome ascertainment or a misspecified model. The registry does not report enough analysis detail to evaluate all such assumptions.

The primary outcome summaries have standard deviations of 1.7 and 2.1. These describe spread in the reported group outcomes, rather than precision of the rate-ratio estimate. The outcome group sizes are 12 and 10, and the trial is listed with enrollment of 28. The registry record does not explain the relationship between enrollment and the outcome analysis group sizes. That missing participant-flow detail also limits assessment of precision and possible selection effects.

The secondary mean-difference intervals are also broad and include zero: -3.688 to 15.69 for the St. George's Respiratory Questionnaire and -5.509 to 15.51 for the Cough-Specific Quality of Life Questionnaire. They allow for differences in either direction. Without the scale direction and an importance threshold, interval width cannot be translated into a judgment about meaningful improvement or worsening. Overall, the estimates are not precise enough to support a confident claim about the direction or size of a group difference.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures describe participants per arm for the continuous-outcome calculations and for the event-rate planning illustration in this record; they are not totals across both groups. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. For time-to-event tables, the record specifies total events, but the posted primary outcome is an event-rate outcome rather than a time-to-event outcome.

For the primary event-rate comparison, the illustration lists 943 participants per arm for 80% power and 1,262 participants per arm for 90% power when planning for 100% of the observed effect. For 75% of the observed effect, it lists 1,693 participants per arm for 80% power and 2,266 for 90% power. For 50% of the observed effect, it lists 3,847 participants per arm for 80% power and 5,150 for 90% power.

In plain language, the 80% power column describes a planning scenario designed to have an 80% chance of detecting the assumed effect if that effect is real and the assumptions hold. The 90% power column uses a higher target chance of detection, which generally requires a larger planned sample under the same assumptions. Smaller effects are harder to distinguish from random variation, so planning to detect a smaller fraction of the observed effect requires more participants.

These values are planning illustrations calculated from the observed effect, not the trial's original design assumptions. The registry record does not report the original sample-size justification. This is not observed power: it does not describe the probability that the completed trial detected an effect, and it cannot resolve the uncertainty in the posted results.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, λ₀ and λ₁ are event rates per patient-year, and T is follow-up per participant in years. This assumes Poisson counts and equal follow-up.

Worked calculation for this trial

1. Control rate λ₀ = 2.3000; treatment rate λ₁ = 2.5000 events per patient-year; follow-up T = 1.00 years.
2. n = (1.96 + 0.842)² × (1/2.3000 + 1/2.5000) / (1.00 × [ln(1.087)]²) = 942.4, rounded up to 943 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
lambda0 <- 2.3                      # control rate, events per patient-year
lambda1 <- 2.5                      # treatment rate
tt      <- 1                       # follow-up per participant, years
n_per_arm <- function(power, frac = 1) {
  l1 <- lambda0 * (lambda1 / lambda0)^frac   # smaller effect = fraction of the observed log rate ratio
  ceiling(round((z_a + qnorm(power))^2 * (1 / lambda0 + 1 / l1) / (tt * log(l1 / lambda0)^2), 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Simulation 1: Poisson counts. Simulation 2: over-dispersed counts (variance = 1.5 x mean), analysed with the matching variance.
set.seed(452114)
n    <- n_per_arm(0.80)
reps <- 20000
m0 <- lambda0 * n * tt; m1 <- lambda1 * n * tt
x0 <- rpois(reps, m0); x1 <- rpois(reps, m1)
z  <- log(x1 / x0) / sqrt(1 / x0 + 1 / x1)
cat(sprintf("Simulated power, Poisson counts, n = %s per arm: %.3f\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE)))
phi <- 1.5
y0 <- rnbinom(reps, mu = m0, size = m0 / (phi - 1)); y1 <- rnbinom(reps, mu = m1, size = m1 / (phi - 1))
z2 <- log(y1 / y0) / sqrt(phi * (1 / y0 + 1 / y1))
cat(sprintf("Simulated power, over-dispersed counts (phi = 1.5), same n: %.3f\n", mean(abs(z2) > z_a, na.rm = TRUE)))

Output from running the code

100% of observed effect: n per arm = 943 (80% power), 1,262 (90% power)
 75% of observed effect: n per arm = 1,693 (80% power), 2,266 (90% power)
 50% of observed effect: n per arm = 3,847 (80% power), 5,150 (90% power)
Simulated power, Poisson counts, n = 943 per arm: 0.796
Simulated power, over-dispersed counts (phi = 1.5), same n: 0.626

The first simulation draws Poisson counts and should land close to the target power. The second allows extra variability (variance 1.5 times the mean, a purely illustrative value), which lowers the power at the same sample size, so rate trials usually need more participants than the Poisson formula suggests.

14. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary exacerbation outcome and two secondary quality-of-life outcomes. It does not report a multiplicity adjustment or a hierarchy for interpreting secondary outcomes. As general statistical explanation, testing multiple outcomes can increase the chance of at least one seemingly unusual result even when no underlying effect is present. Adjustment methods or a prespecified testing sequence can address that issue, but neither is described in the registry record. The secondary p-values are therefore best treated as unadjusted and exploratory.

Missing-data methods are not reported in the registry record. The outcome summaries list 12 participants in the in-exsufflator group and 10 in the flutter-device group, while registry enrollment is 28. The record does not explain participant flow, reasons for any difference between enrollment and outcome group sizes, or whether outcome data were unavailable for some participants. No inference about attrition or its causes can be made from those figures alone.

The analysis population is also not reported in the registry record. It does not say whether the posted comparisons include everyone as randomized, only participants who completed follow-up, or another defined population. The record does not describe how withdrawals, missed assessments, or incomplete event records were handled. These details matter because excluding participants or imputing missing outcomes can affect both estimates and uncertainty.

The registry does not report an original statistical analysis plan, interim analyses, subgroup analyses, or model diagnostics. It also does not state whether any covariates were prespecified for adjustment. These absences do not show that such procedures did or did not occur; they mean they are not documented in the registry record. Without that information, the unadjusted posted comparisons should not be presented as if they were fully characterized sponsor analyses or as definitive tests of the study hypothesis.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The adverse-event figures report no serious adverse events in either listed group and no deaths. The record lists 15 participants at risk for serious adverse events in the in-exsufflator group and 13 in the flutter-valve group. The figures for other adverse events also show no affected participants, with the same group-specific at-risk counts. No serious adverse-event terms are listed.

These are registry-reported counts, not evidence that no adverse events of any kind occurred outside the recorded categories or observation period. The record does not provide event definitions, collection procedures, severity details beyond the serious-event category, or information about duration of safety follow-up. It also does not explain why the at-risk counts differ from the primary-outcome group sizes. The absence of recorded events in these summaries should therefore be read narrowly and does not establish comparative safety.

16. What the Result Does, and Does Not, Mean

The posted primary summaries show mean exacerbation counts of 2.5 per patient in the in-exsufflator group and 2.3 in the flutter-device group over 12 months. The rate ratio is 1.087, and the confidence interval spans values below and above 1. The result is therefore imprecise and does not establish a clear difference between groups. The posted p-value of 0.764 likewise does not provide evidence of a statistically clear difference, but it is not a test of equivalence.

What these data do mean is limited to the reported participants and measures: the registry presents group-level summaries for exacerbations and quality-of-life scores, along with a set of adverse-event counts. The summaries allow a descriptive comparison. They do not reveal individual event patterns, establish why the study was terminated, or show whether every planned outcome was assessed.

What they do not mean is that either device is effective or ineffective, or that the devices are equivalent. A failure to identify a clear difference is not proof that the true effects are identical. The wide uncertainty is compatible with a range of possible effects, and the registry provides no clinically important difference threshold with which to judge their practical meaning. Nor can the secondary results establish a broader health benefit when score direction and meaningful-change thresholds are not reported.

The registry record also does not report details needed to judge the robustness of the comparison, including a complete analysis plan, missing-data approach, analysis population, or model diagnostics. The status is terminated, but the reason for termination is not reported in the registry record. These constraints call for a cautious reading of the posted estimates rather than a causal or clinical conclusion beyond what the summaries support.

17. Why This Trial Matters Statistically

This study is statistically instructive because its primary outcome counts recurrent events, rather than measuring only a single event or a continuous score. Recurrent-event outcomes require attention to both the count distribution and the observation period. A rate ratio communicates a relative comparison, while group means make the underlying event frequency easier to read in context. Neither measure removes the need to assess how events were defined and collected.

The result also illustrates why an estimate and its precision must be considered together. The rate ratio is near 1, but the confidence interval spans the null value and extends to a substantially higher rate. A point estimate alone would conceal that uncertainty. Conversely, a non-significant p-value should not be translated into proof that the groups are the same. The distinction between absence of clear evidence and evidence of equivalence is central to interpreting small or imprecise trials.

The registry's planning illustration further shows that sample-size requirements depend on the effect chosen for planning. Smaller target effects require larger samples under the stated assumptions. Those calculations are separate from the trial's own design justification, which is not reported in the registry record. They should not be mistaken for a retrospective measure of whether the trial was adequately powered.

Finally, reporting completeness shapes statistical interpretation. The record gives group summaries and unadjusted comparisons, but does not document a full analysis plan, multiplicity strategy, missing-data handling, or participant flow. Those are not minor details: they help readers understand how estimates were generated and how broadly they can be generalized. This trial therefore highlights both the value of transparent outcome summaries and the limits of interpretation when analysis and follow-up details are absent.

18. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
• Rate comparisons use a Poisson approximation unless the sponsor posted confidence limits; real event counts are often over-dispersed.

Several limitations specific to this record constrain interpretation. The study is listed as terminated, but the reason for termination is not reported in the registry record. The record lists enrollment of 28, while outcome summaries are based on group sizes of 12 and 10. It does not provide a participant-flow account or explain the relationship between those figures, so the completeness and representativeness of the outcome summaries cannot be assessed.

The primary event-rate comparison is a Poisson-based unadjusted calculation from the posted summaries. The registry does not report model diagnostics, a check for over-dispersion, covariate adjustment, or a detailed analysis plan. It does not describe how exacerbations were defined or ascertained, and it does not report individual event patterns. These gaps make it difficult to evaluate whether the modeling approach reflects the data structure and event process.

The record does not report the study's original sample-size justification, missing-data procedures, analysis population, interim analyses, or multiplicity handling. The secondary questionnaire scales lack reported score direction and clinically meaningful thresholds. Costs and pulmonary function are mentioned in the study summary, but results for them are not reported in the registry record. The posted results are therefore narrower than the range of outcomes mentioned in the study description.

Finally, no masking is listed, and the record does not describe adherence, device training, or other care. These details may be relevant to how the interventions were delivered and outcomes assessed, but their absence from the registry record does not establish what occurred. In combination, these reporting limits mean the estimates should be understood as descriptive, uncertain comparisons rather than complete evidence about the devices or the study's full set of stated aims.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: In-exsufflator Cough Assist Device in Patients With Symptomatic Bronchiectasis — NCT00452114.
• Registry record last updated 2018-09-18; status last verified 2018-08.
• Results first posted 2013-03-06.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

22. Record Summary

The registry describes a randomized, unmasked, parallel-group study comparing daily in-exsufflator cough assistance with a daily flutter valve in symptomatic bronchiectasis. The primary outcome was the number of suppurative exacerbations per patient over 12 months. The posted means were 2.5 and 2.3, with an unadjusted rate ratio of 1.087 and a p-value of 0.764; the confidence interval spans values below and above 1.

Two secondary quality-of-life outcomes are also posted, along with adverse-event counts showing no recorded serious or other adverse events and no deaths in the listed groups. The registry status is terminated. It does not report the reason for termination, the original sample-size justification, or a complete analysis plan. The posted results are descriptive and imprecise, and do not establish a clear difference or equivalence between the device groups.