Music During Labor Epidural Placement and Patient Satisfaction: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Music During Labor Epidural Placement and Patient Satisfaction (NCT02734056), a randomized na study. The primary outcome is Anxiety.

2. Clinical Question

The record identifies anxiety as the primary outcome and reports a mean score for each group. The music group’s reported mean was 2.9, compared with 1.4 in the control group. The posted unadjusted mean difference is 1.5 points in the direction of a higher score in the music group. This is a comparison of the recorded group averages; by itself, it does not explain why scores differed or establish how the experience varied among individual participants.

The registry summary describes the research question as examining patient-preferred music and satisfaction in women undergoing labor epidural placement. However, the registered primary outcome is anxiety, not a satisfaction score. The registry record does not report a separate posted satisfaction outcome. The outcome description says that questions were scored and combined into a composite score, but it does not give the individual questions or explain the construction of that composite.

3. Trial Design

The registry identifies this as a randomized, parallel-group trial with no masking. Participants were assigned to a music group or a control group. The music group received music; the control group had no intervention listed. Because masking is recorded as none, the registry does not indicate that participants or study personnel were masked to assignment.

The record lists an enrollment of 100. For the anxiety outcome, the posted summaries report 50 participants in the music group and 49 in the control group. These outcome counts are the numbers attached to the reported group summaries; they should not be treated as an explanation of who was enrolled, excluded, or included in each analysis. The record does not report a participant flow account or reasons for any difference between enrollment and outcome counts.

The trial is marked completed. The listed start was 2015-10, and the listed primary completion was 2016-01. Its phase is recorded as not applicable. Brigham and Women's Hospital is listed as the sponsor. These registration details establish the record’s design and administrative context, but do not provide the full protocol or a detailed account of how the trial was conducted.

Random allocation is intended to create groups that are comparable on average, including on factors that are not measured, but it does not guarantee that every characteristic will be balanced in a particular trial. The registry record does not describe the sequence-generation method, allocation concealment, implementation of randomization, or any baseline characteristics. It also does not provide details about adherence to the assigned intervention. Consequently, the posted group comparison can be described, while the available record does not permit a fuller assessment of those design features.

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

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 Anxiety, measured over 1 hour.

The primary endpoint is anxiety measured one hour after the intervention period. The registry describes a composite score formed by scoring questions and combining them. The unit is a score on a numeric rating scale from 0 to 10: 0 represents no anxiety and 10 represents the worst anxiety. A continuous score allows the group results to be summarized as means and standard deviations, which describe the average score and the spread of scores around that average.

Anxiety is relevant to the stated study context because the trial concerns music during labor epidural placement, and the registry summary frames the research around patients’ experiences. The posted primary measure specifically captures anxiety, however, and should not be read as a direct measurement of overall satisfaction. A scale can provide a standardized way to summarize responses, but its interpretation also depends on its questions, scoring, timing, and validity for the population and setting.

The one-hour timeframe gives a defined point at which the registry intended to assess the outcome. The record does not specify the exact timing reference for that hour, the individual questions in the composite, how missing answers were handled, or whether the scale was validated for this use. It also does not report a threshold for interpreting a score difference as important to patients. The posted results therefore support a description of the measured group averages, but not a conclusion about the clinical importance of the difference.

7. Results Posted in the Registry

• Music: mean 2.90 versus 1.40 on control; difference 1.50 (95% CI 0.47 to 2.53), standardized effect d = 0.57; z-test p = 0.004.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant’s composite anxiety score is a number on a 0-to-10 scale. The registry reports a mean and standard deviation for each group. The mean describes the arithmetic average of the scores. The standard deviation describes how dispersed scores are around that mean; a larger standard deviation indicates more variability in the observed scores, not greater uncertainty in the mean by itself. The music group’s reported spread is wider than the control group’s, so the two sets of scores were not equally dispersed in the summaries.

What does the mean difference represent?

The posted mean difference is 1.5 points, calculated in the stated direction of music minus control. It is the difference between the two reported group averages, not a change from baseline and not the score difference experienced by each participant. A group-level contrast can coexist with substantial overlap in individual scores. The record does not report baseline anxiety scores, so the result should not be described as a change in anxiety over time.

The posted comparison also includes a pooled standard deviation and a standardized effect-size estimate. Standardizing a mean difference expresses it in relation to the variability of scores, which can help compare measures that use different units. Those statistics depend on the chosen standardization method and its assumptions. The registry record does not describe that method, so the standardized estimate should not be treated as a substitute for the original score difference or given a clinical interpretation on its own.

How should the p-value be understood?

The unadjusted p-value is 0.004. In general, a p-value is calculated under a null hypothesis and a statistical model; it quantifies how unusual data at least as incompatible with that null would be if the model and null hypothesis were correct. It does not give the probability that a treatment has an effect, and it does not show the probability that the result will replicate. A smaller p-value is not necessarily a larger effect or a more important effect.

The specific statistical test, whether it allowed for unequal variances, and any analysis details are not reported in the registry record. Although the posted group summaries permit a simple unadjusted comparison to be described, the method used by the trial team cannot be reconstructed from the information in the record. The p-value is therefore presented as the posted unadjusted result, without assigning it to an unreported test.

What does randomization contribute?

In general, random assignment aims to reduce systematic differences between groups at the point of assignment. If assignment and follow-up are conducted appropriately, it can support an interpretation of the between-group contrast as an effect of assignment. Randomization does not guarantee equal group characteristics in a particular sample, and it does not address biases caused by missing outcomes, deviations from assignment, measurement, or selective reporting.

The record describes the allocation as randomized and the model as parallel, but it does not report the random sequence method or allocation concealment. Masking is recorded as none. The record also does not describe adherence, departures from assigned groups, or a primary analysis population. These omissions limit how completely the assumptions behind a causal interpretation can be checked.

Why does score variability matter?

When a continuous measure has substantial variation, individual scores may differ considerably even when group means differ. The standard deviation is a descriptive measure of that variation. In general, more variability makes the mean difference less precisely estimated when other features, including sample size, are held fixed. Unequal variability between groups can also matter for the choice and behavior of a statistical method. The record gives group standard deviations, but it does not state whether the comparison method assumed equal variances or used an alternative approach.

The composite-score description is brief. The registry says questions were scored and a composite determined, but it does not describe the questions, their weighting, or rules for incomplete responses. Without such information, readers cannot assess how closely the score captures anxiety or how a particular response pattern translated into the final score. These measurement considerations are separate from the statistical uncertainty around the group means.

What is the role of the confidence interval?

In general, a confidence interval gives a range of estimates compatible with the observed data under a specified method and its assumptions. The posted interval for the mean difference is 0.469 to 2.531. It describes uncertainty in the estimated group contrast, rather than the range containing most participants’ scores. It is also not a guarantee that the true difference lies within the particular interval. Its interpretation depends on the statistical procedure, which is not detailed in the registry record.

The confidence interval and p-value address related but distinct questions. The interval emphasizes the range and precision of plausible values under the method; the p-value quantifies compatibility with a null value under a test. Neither statistic resolves questions about clinical importance, outcome validity, missing data, or generalizability. For those questions, the result must be considered alongside the measure, trial design, and reporting limitations.

10. Confidence Intervals and Precision

The point estimate for the unadjusted mean difference is 1.5 points. The posted confidence interval extends from 0.469 to 2.531 points. Because the interval does not include zero, the range of values represented by this interval is consistent with a positive mean difference under the analysis method. The endpoints convey uncertainty around the average contrast; they do not describe the range of individual anxiety scores.

Precision is different from magnitude. The estimate gives the observed size and direction of the group contrast, while the interval indicates how much uncertainty surrounds that estimate under the method used. A confidence interval is not a guarantee about the location of the true effect, and it does not account for sources of uncertainty that the analysis did not include. In particular, the registry record does not describe the statistical procedure used to form the interval, nor does it give enough information to assess possible effects of missing data, measurement limitations, or deviations from the intended design.

The group standard deviations provide context for the interval: observed scores varied within both groups, and the reported variability was greater in the music group. A mean contrast can be estimated even when scores vary considerably, but the interval reflects uncertainty in the contrast, not the experience of any one participant. The record does not state a threshold for a meaningful change on this composite, so the interval alone cannot determine whether its values would represent an important difference to patients.

The confidence interval is posted alongside an unadjusted p-value of 0.004. These statistics tell related parts of the inferential story, but neither measures the probability that the result is correct. Their interpretation depends on the model and test assumptions, which are not fully reported. The interval should therefore be read as precision under the posted analysis, rather than as a complete accounting of uncertainty about the trial question.

11. 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 are illustrations based on the observed mean difference, not the trial’s original design calculations. They give participants per arm, rather than a total number of events. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is set as a stated fraction of the observed effect.

At 100% of the observed effect, the illustration gives 49 participants per arm for 80% power and 65 participants per arm for 90% power. At 75% of the observed effect, it gives 86 participants per arm for 80% power and 116 participants per arm for 90% power. At 50% of the observed effect, it gives 194 participants per arm for 80% power and 259 participants per arm for 90% power.

In plain terms, the 80% power column describes the planning number associated with an 80% chance of detecting the specified effect under the stated assumptions, if that effect is present and the model assumptions hold. The 90% power column uses a higher detection probability and consequently lists larger planning numbers for each effect fraction. These are planning calculations, not observed power.

The illustrations show why smaller effects need more participants: a smaller difference is harder to distinguish from ordinary variation, so the calculation requires more participants under the same assumptions. The observed effect may not be the effect a future study should expect to detect. The registry record does not report the original sample-size justification or the assumptions used to plan this trial, so these illustrations should not be taken as evidence about the trial’s own design target.

12. 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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 1.500; pooled standard deviation σ = 2.633.
2. n = 2 × (1.96 + 0.842)² × 2.633² / 1.500² = 48.4, rounded up to 49 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
delta <- 1.5                      # observed difference in means
sigma <- 2.63272427599285                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2734056)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 49 (80% power), 65 (90% power)
 75% of observed effect: n per arm = 86 (80% power), 116 (90% power)
 50% of observed effect: n per arm = 194 (80% power), 259 (90% power)
power.t.test: 49.3 
Simulated power at n = 49 per arm: 0.802 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure, anxiety, and no posted secondary outcomes. It lists zero analyses. The comparison associated with the primary measure is unadjusted, and no multiplicity adjustment is reported. With only one posted outcome comparison, the record does not describe a family of posted tests requiring a stated adjustment; however, it also does not provide a complete analysis plan or establish whether additional analyses were conducted but not posted.

Multiplicity arises when many outcomes, time points, subgroups, or analytic choices are examined. In general, repeated testing can increase the chance of seeing at least one apparently unusual result even when there is no underlying effect. A prespecified analysis plan can clarify which outcome and contrast are primary and how additional analyses will be treated. The registry record does not report such a plan, interim analyses, or a multiplicity strategy. No claims about those procedures can be made from the posted information.

Missing-data handling is not reported in the registry record. The record does not say whether every randomized participant posted an anxiety score, how incomplete composite scores were handled, or whether any imputation or sensitivity analysis was used. The outcome summaries report 50 participants for music and 49 for control, while the registered enrollment is 100. These registry entries do not establish why the counts differ or whether missing outcome data occurred. A participant flow account and explicit analysis denominators are not reported.

The analysis population is also not reported in the registry record. It is not specified whether participants were analyzed according to randomized assignment, whether any participants were excluded after assignment, or how adherence was treated. These choices can affect the interpretation of a randomized comparison. Without the analysis population and missing-data details, the result is best described as the posted unadjusted comparison of the reported outcome summaries, rather than as a fully documented intention-to-treat or per-protocol analysis.

The record does not describe the statistical plan, model specification, or any prespecified handling of outliers or distributional features. These omissions do not invalidate the posted numerical summaries, but they limit independent assessment of how the primary comparison was selected and carried out. No conclusions should be drawn about unreported analyses or procedures.

14. 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 registry’s adverse-event record lists zero serious adverse events and zero other adverse events for the music group, and zero of each for the control group. The adverse-event entries list 50 participants at risk in each group. These are the recorded figures in the registry, not an independently verified account of all events during the trial.

The adverse-event denominators differ from the anxiety outcome summaries, which report 50 participants in the music group and 49 in the control group. The registry record does not explain the difference. It also does not provide event definitions, collection procedures, observation duration, or further detail about how adverse events were monitored. No serious adverse-event terms are listed, and the death count is zero in both groups.

Zero recorded events should be read as the counts posted in this record, not as proof that no events occurred under every possible definition or observation window. The available information does not describe the completeness of safety ascertainment, so the adverse-event entries should be interpreted narrowly and in the context of the limited reporting.

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

The posted results show a higher mean anxiety score in the music group than in the control group at the one-hour assessment: 2.9 compared with 1.4. The unadjusted mean difference is 1.5 points, and the posted confidence interval is 0.469 to 2.531. The unadjusted p-value is 0.004. These figures describe the recorded primary outcome and the uncertainty represented by the posted comparison.

They do not establish that music caused the observed score difference. Randomization is part of the design, but the registry record does not provide enough detail about allocation procedures, follow-up, analysis populations, missing data, adherence, or the statistical method to evaluate every assumption needed for a causal interpretation. The result is also limited to the anxiety composite at the recorded time point and does not establish a difference in patient satisfaction or other outcomes.

The scale ranges from 0 to 10, with higher scores representing worse anxiety, but the registry does not report a threshold for a patient-important difference. Statistical evidence about a group average does not by itself establish clinical importance. Nor does the mean difference describe the range of individual experiences: the reported standard deviations indicate that scores varied within both groups, particularly in the music group.

The record describes the study as involving patient-preferred music, but the intervention description itself only identifies music and does not explain whether participants selected it or how it was delivered. The results therefore should not be generalized to other music approaches, settings, populations, or time points based on this record alone. The absence of posted secondary outcomes also means that the primary anxiety comparison should not be treated as a comprehensive account of the trial’s stated interest in satisfaction.

The most defensible reading is descriptive: the reported group averages differed in the direction of a higher anxiety score for the music group, with an unadjusted interval and p-value indicating statistical uncertainty under an analysis whose details are not reported. The findings do not provide medical advice or determine what any individual should choose.

16. Why This Trial Matters Statistically

This trial illustrates the distinction between a study’s broad motivation and its registered primary endpoint. The registry summary discusses patient satisfaction, but the primary outcome posted for analysis is anxiety on a numeric rating scale. Keeping those constructs separate matters: an anxiety score is not interchangeable with a satisfaction measure, even when both relate to patients’ experiences of care.

It also shows why a mean difference should be considered alongside variability and precision. The group means indicate the direction and magnitude of the average score contrast, while the standard deviations describe the spread of scores and the confidence interval describes uncertainty around the contrast. Those statistics answer different questions. None alone shows how individual participants experienced the intervention or whether the difference was meaningful to them.

Randomized allocation provides a design framework for comparing groups, but useful interpretation also depends on transparent reporting of how allocation was implemented, who contributed outcomes, how missing data were addressed, and which analysis was prespecified. The registry record does not report those details. This makes clear that a concise numerical result is not a substitute for a full account of trial conduct and analysis.

The planning illustrations further distinguish a design calculation from a trial finding. Their numbers are derived from the observed effect under stated assumptions; they do not explain the original enrollment target or the planning rationale for this trial. Because smaller effects require larger planning numbers under the same assumptions, planning depends strongly on which effect is considered worth detecting. That choice is substantive as well as statistical.

Finally, the posted safety counts demonstrate the importance of reading denominators and event definitions alongside zero counts. The adverse-event entries and outcome summaries use different reported group counts, and the record does not explain why. Accurate statistical interpretation therefore includes attention to what is reported, what is not, and what each number actually represents.

17. 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.

The registry record leaves important trial details unspecified. It does not report eligibility criteria beyond the described population, participant characteristics, baseline anxiety, or a flow account. This makes it difficult to judge how participants entered the analysis or how representative they were of women undergoing labor epidural placement more broadly.

The intervention description is brief. It identifies music but does not explain its selection, delivery, duration, or fidelity. The control group is described as having no intervention, and masking is recorded as none. The record does not describe whether outcome assessors were masked or whether participants’ awareness of assignment could have influenced their responses on the anxiety scale.

The outcome is described as a composite of scored questions, but the questions, scoring rules, validation, and handling of incomplete responses are not reported. The one-hour timeframe is given without further explanation of the timing reference. The record also does not identify a threshold for a clinically important difference. These omissions limit interpretation of what a score contrast means beyond the numeric scale.

The anxiety summaries report 50 participants for music and 49 for control, whereas enrollment is listed as 100. The record does not explain the participant accounting. The adverse-event summaries list 50 participants at risk in each group, which also differs from the outcome summaries. Missing-data procedures and analysis populations are not reported, so the implications of these counts cannot be determined.

The statistical test, model details, prespecified analysis plan, and multiplicity approach are not reported. The posted p-value is unadjusted. There are no posted secondary outcomes or analyses in the record, and no information about interim analyses. The confidence interval and p-value can be described, but the record does not permit a full independent review of how they were calculated or whether other analyses were planned or conducted.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Music During Labor Epidural Placement and Patient Satisfaction — NCT02734056.
• Registry record last updated 2017-03-30; status last verified 2017-03.
• Results first posted 2017-03-30.
• 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.

21. Record Summary

The registry record describes a completed, randomized, parallel-group trial with no masking, comparing music with a control condition during labor epidural placement. The primary outcome is a composite anxiety score measured one hour later on a numeric rating scale from 0 to 10, with higher values indicating worse anxiety.

The posted outcome summaries report a mean of 2.9 and standard deviation of 3.3 for the music group, and a mean of 1.4 and standard deviation of 1.7 for the control group. The unadjusted mean difference is 1.5 points, with a posted confidence interval of 0.469 to 2.531 and p-value of 0.004. The registry lists no posted secondary outcomes and zero analyses.

Interpretation is limited by unreported details about outcome measurement, participant accounting, missing data, analysis populations, statistical methods, and trial procedures. The adverse-event record lists zero serious and zero other adverse events in each group, with 50 at risk in each group.