Project Quit: Positive vs. Negative Offers of an Online Stop Smoking Program: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Project Quit: Positive vs. Negative Offers of an Online Stop Smoking Program (NCT01923467), a na na study. The primary outcome is Acceptance of Offer to Join Stop Smoking Program.

2. Clinical Question

The central statistical question is about uptake of an offer, not whether participants subsequently quit smoking. The primary outcome is recorded as the number of participants accepting the offer, with assessment described as occurring 1 Day of Enrollment. This is a behavioral response to the study invitation. It does not, by itself, establish whether participants began the program, completed it, or changed their smoking behavior.

The summary describes a 2x3 design intended to assess affirmation and three image types. It identifies aims concerning affirmation, image type, and their interaction. Those aims describe the comparisons of interest, but the registry record does not give outcome counts by condition or estimates of those effects. It therefore does not establish which conditions had greater uptake, or whether the factors acted independently or jointly.

3. Trial Design

Project Quit is recorded as completed, with enrollment of 767. The registry lists the study as a single-group model and allocation as NA, while the summary describes a 2x3 design involving affirmation and positive, neutral, or negative imagery. These descriptions do not establish how participants were assigned to conditions. The allocation procedure and condition-specific enrollment are not reported in the registry record.

The study summary says participants viewed images and completed writing reflection tasks, after which they were asked whether they wished to take part in an online stop-smoking program. Its stated aims concern acceptance of that offer and possible effects of affirmation, image type, and their interaction. The registered primary outcome is assessed at 1 Day of Enrollment. The record does not give a longer follow-up interval for this primary measure.

The registry lists a behavioral intervention named Project Quit stop smoking program and a drug intervention named nicotine patches 21 mg. The listed arm is Project Quit Plus NRT Patches. Its description says participants in the program would be offered the online program and begins to describe an offer of patches to eligible participants, but the registered arm description is incomplete. Further details about eligibility, the patch offer, and the relationship between these interventions and the image and affirmation conditions are not reported in the registry record.

The study dates are recorded as 2013-08 for start and 2014-04 for primary completion. The registry does not provide a detailed protocol, a participant flow, or condition-level enrollment figures. Because the listed model and allocation do not document a randomized comparison, condition effects should not be interpreted as randomized treatment effects on the basis of this record.

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.

Population: Smoker recruited from an online survey panel.

6. Primary Endpoint

The registry lists the primary outcome as Acceptance of Offer to Join Stop Smoking Program, measured over 1 Day of Enrollment.

The primary endpoint is titled “Acceptance of Offer to Join Stop Smoking Program.” It measures the number of participants who say they would like to take part in an online stop-smoking program after completing online image viewing and writing reflection tasks. The stated assessment time is 1 Day of Enrollment. The registry describes the outcome as a number of participants, rather than a measure of smoking cessation.

Acceptance is relevant to the study’s stated aims because those aims ask whether affirmation or image type changes uptake of an offer. A response at this point captures willingness to join, which is a decision close to the message and invitation being studied. It is not equivalent to enrollment in the program, completion of the program, participation over time, or a successful quit attempt. Those later outcomes would require their own definitions and observations; the primary endpoint description does not provide them.

The endpoint title and description define what was intended to be measured, but the registry record does not report the observed acceptance counts, condition-specific results, or an estimated contrast between conditions. It also does not explain how responses were handled if a participant did not answer the question. Without the outcome results and analysis details, the endpoint can be interpreted as a planned measure of offer acceptance, but not as evidence about the magnitude or direction of any effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical question described by the study is whether affirmation and image type are associated with acceptance of an offer to join an online stop-smoking program. The summary names three aims: an affirmation effect, an image-type effect across positive, neutral, and negative imagery, and an interaction between image type and affirmation. These aims imply several kinds of contrasts. However, the registry record does not provide the analysis plan or results for any of them.

What does the factorial description imply?

In general, a factorial design studies multiple factors in the same experiment. A main effect describes the average association of one factor with the outcome across levels of another factor. An interaction asks whether the association for one factor changes according to the level of another. An interaction is not simply another name for either main effect; it concerns whether the combined pattern differs from what would be expected from the factors considered separately.

The summary calls the intended design 2x3, but the registry record does not identify the affirmation conditions in detail, explain the assignment procedure, or provide outcome results for the combinations. It also records a single-group model and allocation as NA. A factorial interpretation may explain the stated aims, but it does not resolve how participants actually entered conditions or whether the planned comparisons were carried out.

What would an analysis of acceptance require?

The endpoint is recorded as a number of participants accepting the offer. For a binary response such as acceptance or non-acceptance, a statistical analysis could compare the counts or the probability of acceptance across defined conditions. The choice of effect measure and model would depend on the design, the data structure, and the prespecified analysis plan. Those details, along with the actual counts, are not reported in the registry record. No effect estimate can therefore be interpreted from this entry.

General statistical explanation: an estimate based on observed counts is subject to sampling variability. A confidence interval communicates uncertainty around the estimate, and a wider interval generally indicates less precision. A test of a null hypothesis may produce a p-value, but that value is meaningful only in relation to the stated hypothesis, analysis method, and assumptions. The registry record reports no confidence interval or p-value for acceptance, and does not state which model or test was used.

Why does allocation matter?

Allocation describes how participants enter comparison conditions. Random allocation, when implemented and documented, can support causal comparisons by balancing measured and unmeasured participant characteristics on average. A nonrandom or unclear allocation can leave condition differences entangled with differences in who entered each condition. Here, allocation is recorded as NA and the model as single group, while the summary describes multiple planned conditions. Since the assignment method is not reported in the registry record, the strength of any causal interpretation cannot be evaluated.

How should the planning assumptions be read?

The record describes sample-size planning illustrations using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. These are planning assumptions, not evidence that the study used equal allocation, and not a report of a prespecified trial design. No illustration results or observed effect are included in the record.

General statistical explanation: a planning calculation asks how much information a future or planned study would need under specified assumptions. If the target effect is smaller, more information is generally needed to distinguish it from random variation, all else equal. Such a calculation depends on the assumed effect, outcome variability, error rate, allocation, and analysis method. It is not “observed power,” and it cannot establish whether a result is reliable after data have been collected. The record’s illustrations should therefore be treated as planning aids rather than study findings.

For count outcomes, over-dispersion can matter when observed variability exceeds what a chosen model expects. In general, a model that assumes less variation than the data contain can understate uncertainty and make evidence look more precise than it is. Conversely, an appropriate model can account for extra variation. The primary endpoint is described as a participant count, but the registry record does not provide the data or identify a count model, so there is no basis to assess over-dispersion or model fit for this outcome.

The sample-size assumptions also refer to two arms, whereas the study summary describes a 2x3 design. The record does not explain how the planning illustrations map to the intended comparisons, or whether they were used when the study was designed. No protocol-based sample-size justification is reported in the registry record. These gaps prevent a check of whether the planning assumptions match the study’s actual allocation and analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Project Quit Plus NRT Patches")
n      <- c(767)
events <- c(288)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Project Quit Plus NRT Patches  767  288  37.5  34.1  41.1  34.2  41.0  34.2  41.0

11. Multiplicity, Missing Data and Analysis Populations

The study summary identifies several aims involving affirmation, image type, and their interaction. When a study evaluates multiple hypotheses, the chance of at least one false-positive finding can increase if each is tested separately without an adjustment or a prespecified hierarchy. General statistical practice may address multiplicity through adjustment, prioritization of hypotheses, or a clearly defined primary comparison. The registry record does not report a multiplicity strategy, a hierarchy among the aims, or an analysis plan. It is therefore not possible to determine how the several stated questions would be handled in inference.

The record identifies a primary endpoint, acceptance of the offer, but gives no primary-endpoint results or analyses. It does not describe any secondary outcome results in the posted entry. The analysis populations—such as which participants were included in each analysis and how eligibility or missing responses were handled—are not reported in the registry record.

Missing data are also not described. The entry does not report how many participants answered the acceptance question, whether any responses were incomplete, or how missingness was addressed. General statistical explanation: missingness can affect an estimate when the probability of observing an outcome is related to participant characteristics or the outcome itself. An analysis that excludes missing observations may not answer the same question as an analysis that accounts for them. Without the response and missingness information, the extent or direction of any such concern cannot be assessed.

The absence of these details is not evidence that a particular method was or was not used. It means the registry entry does not support evaluation of multiplicity control, missing-data handling, or the analysis populations.

12. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The adverse-event entry lists 0 serious adverse events among 767 at risk and 0 other adverse events among 767 at risk for Project Quit Plus NRT Patches. These are the counts recorded in the registry. The death count is not reported in the registry record, and no serious adverse-event terms are listed.

These figures should be read as registry-recorded event counts for the listed group, not as a comparison between treatment conditions. The entry does not supply a control-group safety comparison, participant-level event details, or information about how events were collected and monitored. It also does not explain the relationship between the safety group and the image and affirmation conditions. Therefore, the counts do not allow a comparative estimate of safety across those conditions.

General statistical explanation: an event count is a description of what was recorded, while an event rate or comparative risk requires a clearly defined observation period and suitable denominators for each group. A zero recorded count does not by itself establish that an event is impossible or that the data rule out uncommon events. No event rates or comparative safety estimates are reported in the registry record, and none can be inferred from the listed counts alone.

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

The record establishes that Project Quit was registered to study smokers’ responses to an offer of an online stop-smoking program after image viewing and writing reflection tasks. It specifies acceptance of the offer as the primary outcome and describes aims related to affirmation, image type, and their interaction. The study is marked completed, and enrollment is 767.

What the posted record does not establish is whether acceptance differed across conditions, how large any difference was, or how precisely it was estimated. There are no posted outcome counts, estimates, confidence intervals, p-values, or analyses for the primary endpoint. The study’s stated aims should not be mistaken for findings: an aim identifies a question, not its answer.

Acceptance is also narrower than cessation. Saying yes to an offer is not the same as enrolling, using a program, completing it, or quitting smoking. The primary endpoint description concerns the response after the online tasks, and it does not provide evidence about later smoking outcomes. Although the registry lists a stop-smoking program and nicotine patches 21 mg, the incomplete arm description and absent analysis results do not permit conclusions about their effects.

General statistical explanation: an inconclusive or missing report is not the same as evidence of no effect. To assess whether data are compatible with no difference, readers need the estimated contrast and its uncertainty. To assess whether an effect might be meaningful, they also need to consider its size and the context of the outcome. Those quantities are not reported in the registry record. The appropriate conclusion is therefore limited: the entry documents the study question and planned endpoint, but does not provide posted results that answer the question.

14. Why This Trial Matters Statistically

This trial is statistically interesting because its stated question concerns both separate effects and a possible interaction. The summary asks whether affirmation changes acceptance, whether positive, neutral, or negative imagery changes acceptance, and whether the imagery effect depends on affirmation. These are related but distinct questions. An analysis focused only on average effects could miss a pattern in which an image condition is associated with different responses under different affirmation conditions.

The case also illustrates why the design description matters before interpreting comparisons. The summary describes a 2x3 design, while the registry classifies the study as single group and gives allocation as NA. Those labels do not document how conditions were assigned. Without that information and condition-level outcome data, the intended contrasts cannot be evaluated as causal effects.

The choice of acceptance as the primary endpoint is statistically aligned with the immediate question of uptake: it captures a response to the offer. At the same time, it is not a substitute for later participation or smoking outcomes. Clear distinction between an intermediate behavioral response and a later clinical or behavioral outcome helps keep conclusions tied to what was measured.

Finally, the registry illustrates the difference between a study’s aims and its reported evidence. A completed status and enrollment figure do not provide an effect estimate. Without posted outcome results, readers cannot judge the magnitude, precision, or statistical evidence for the stated comparisons. The record’s planning assumptions likewise do not replace analysis results or show observed power. These distinctions are central to interpreting clinical and behavioral research responsibly.

15. 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 main limitation for statistical interpretation is the absence of primary-endpoint results. The registry record does not report acceptance counts, condition-specific outcomes, estimates, confidence intervals, or p-values. As a result, it is not possible to assess the direction, size, or precision of the planned comparisons.

The design information is incomplete and internally difficult to reconcile: the summary describes a 2x3 design, whereas the registered model is single group and allocation is NA. The assignment procedure, condition-level enrollment, and precise relationship between the stated factors and the listed arm are not reported in the registry record. These omissions limit assessment of comparability and causal interpretation.

The primary outcome is an immediate response to an offer, assessed at 1 Day of Enrollment. The record does not provide later outcome results or enough detail to determine whether acceptance led to program participation or smoking cessation. It also does not report the endpoint’s missing-response handling, the analysis population, or participant characteristics that would help assess representativeness.

The intervention description is incomplete. The registry lists Project Quit and nicotine patches 21 mg, but the arm description ends before all details are available. The relationship between these interventions, eligibility, and the message conditions is therefore unclear. The entry also does not report the statistical analysis plan, sample-size justification, or approach to the multiple stated aims. These limitations concern what can be established from the registry record; they do not establish that the study did not collect or analyze additional information elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Project Quit: Positive vs. Negative Offers of an Online Stop Smoking Program — NCT01923467.
• Registry record last updated 2015-06-15; status last verified 2014-12.
• Results first posted 2015-06-15.
• 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.

19. Record Summary

Project Quit: Positive vs. Negative Offers of an Online Stop Smoking Program is recorded as completed, with enrollment of 767. The registry lists smoking cessation as the condition and the University of Michigan as sponsor. The study dates are 2013-08 for start and 2014-04 for primary completion.

The summary describes a 2x3 study of affirmation and positive, neutral, or negative imagery, with aims concerning acceptance of an offer to join an online stop-smoking program and an interaction between the factors. The primary outcome is acceptance of that offer, described as a number of participants and assessed at 1 Day of Enrollment.

The registry records a single-group model and allocation as NA, and lists the study as completed. It reports 0 analyses and does not include primary outcome results. Therefore, the record documents the study question and endpoint but does not provide evidence about the observed effects of affirmation or image type on acceptance.