Comparing the Effect of Online and Conventional Oral Health Education in Egypt: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparing the Effect of Online and Conventional Oral Health Education in Egypt (NCT05570500), a randomized na study. The primary outcome is Effect of Oral Health Education on the Oral Health Knowledge in Primary School Children Aged 7-9 Years Old.

2. Clinical Question

The study’s stated aim was to compare the two education approaches in relation to oral hygiene knowledge and practice. The registry describes classrooms in each grade as randomly assigned to the online or conventional group. It also says that a questionnaire assessing knowledge and attitude toward self oral care would be administered before and after the education sessions. The primary outcome, however, is knowledge measured using a score from 0 to 6, with higher scores representing more correct answers.

The registry’s primary outcome description says participants in both arms received an oral health education session through colorful images and cartoons. How those materials relate to the two assigned methods is not explained in the registry record. The clinical question is therefore a comparison of the recorded knowledge scores between the two assigned groups, rather than a comparison of education with no education.

3. Trial Design

This was a randomized, parallel-group study with single masking, recorded as completed. The registry lists enrollment of 636 and names Ain Shams University as the sponsor. The study took place in two schools in Egypt and involved children in 3rd and 4th grade. According to the study description, classrooms in each grade were randomly assigned to online or conventional oral health education.

The registry’s group results list 312 participants in the conventional group and 312 in the online group. These are the group sizes accompanying the posted primary outcome results; the registry record does not explain how they relate to the overall enrollment entry. The masking designation is “single,” but which participants, study staff, or assessors were masked is not reported in the registry record. Details of allocation concealment are also not reported in the registry record.

The study start date is 2022-12-12, and primary completion is listed as 2023-03-20. The primary outcome timeframe is 2 months. The registry describes pre- and post-education questionnaires, but the reported group means do not specify whether they represent post-education scores, change from baseline, or another analysis of the questionnaire measurements. That distinction is not reported in the registry record.

The listed intervention is behavioral oral health education. The registry includes one secondary outcome concerning oral hygiene measures practice, but detailed results for that outcome are not given in the posted primary outcome data. Protocol details such as the planned statistical model, handling of classroom-level assignment in the analysis, and the original sample-size rationale are not reported in the registry 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:

Analysis population for the primary outcome, as defined in the registry: all participants in both arms received oral health education session through colorful images and cartoons.

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 Effect of Oral Health Education on the Oral Health Knowledge in Primary School Children Aged 7-9 Years Old, measured over 2 months.

The primary endpoint is the level of oral health knowledge measured with a questionnaire. Its score is the total number of correct answers in the questionnaire’s knowledge section. That section contains 5 questions: 4 single-answer questions and 1 multiple-answer question with two correct answers. The total score ranges from 0 to 6, and the registry states that higher scores represent better outcomes.

The endpoint is expressed as a mean, with standard deviation used to describe the spread of scores in each group. A mean gives the average score across participants in a group; the standard deviation describes how dispersed individual scores are around that average. The registry specifies a 2 months timeframe. It does not report additional details about the exact assessment date or how questionnaire scoring was checked.

A knowledge score provides a numerical measure that can be compared between the assigned education groups. The registry’s description says that higher mean values of correct answers indicate a satisfactory outcome and lower mean values an unsatisfactory outcome. The reported group results are 2.71 for conventional education and 0.81 for online education. The registry record does not provide a threshold that separates satisfactory from unsatisfactory scores, so these averages should be read as scale values rather than as counts of participants meeting a defined success criterion.

The study also names oral hygiene practice as a secondary outcome. The details and results for that measure are not included with the posted primary outcome results.

7. Results Posted in the Registry

• Comparison Group, Online Oral Health Education Group: mean 0.81 versus 2.71 on control; difference -1.90 (95% CI -2.11 to -1.69), standardized effect d = -1.40; z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean difference describe?

The primary outcome is continuous: each participant receives a knowledge score on a scale from 0 to 6. A group mean summarizes the average score, while the standard deviation summarizes how scores vary around that mean. The posted means are 2.71 in the conventional group and 0.81 in the online group. The reported mean difference is -1.9 for online compared with conventional education. This is an unadjusted contrast in the original scale units, so it can be read as a comparison of the average scores without a reported adjustment for other variables.

General statistical explanation: when a difference is calculated in a stated direction, its sign identifies which group has the larger mean. A negative online-minus-conventional difference corresponds to a lower mean in the online group. The size of the difference is expressed in knowledge-score points, not as a percentage or proportion.

What does the standard deviation add?

The conventional group’s standard deviation is 1.53, and the online group’s is 1.16. These values describe participant-to-participant spread in the scores. They are not confidence limits for the means and are not standard errors. A standard error instead describes the sampling uncertainty of an estimate, and the registry lists separate standard errors for the two group means: 0.087 for conventional education and 0.066 for online education.

General statistical explanation: standard deviations help readers understand whether individual observations cluster near a mean or are more widely dispersed. In a bounded score scale, the possible range also matters to interpretation; this knowledge score cannot be below 0 or above 6. The registry does not give the score distribution or the number of participants at each score.

How should the interval and p-value be read?

The reported confidence interval for the mean difference runs from -2.113 to -1.687. It communicates uncertainty around the estimated difference under the method used to construct it. The confidence level and the exact analysis method are not reported in the registry record. The unadjusted p-value is <0.001. “Unadjusted” indicates that the registry labels this p-value without an adjustment for multiple comparisons; whether any other adjustment or modeling was used is not reported in the registry record.

General statistical explanation: a confidence interval and a p-value answer related but different questions. An interval gives a range of estimates compatible with a method and its assumptions; a p-value assesses compatibility of the data with a specified null model. Neither one establishes causation or practical importance on its own. Interpretation also depends on whether the analysis respects the design and outcome measurement.

Why does the assignment structure matter?

The registry says classrooms were randomly assigned to the two groups. Participants in the same classroom may share features of their learning environment, so their outcomes may be more alike than outcomes from participants in different classrooms. General statistical explanation: when observations are grouped or clustered, an analysis that treats every participant as fully independent can misstate uncertainty if the clustering is not addressed. The registry record does not report the number of classrooms, the analysis unit, or whether a statistical method accounted for classroom-level assignment. The posted comparison should therefore be interpreted with that reporting gap in mind.

Random assignment can support a fair comparison when the allocation process and subsequent analysis are appropriately handled. But the registry record does not report allocation concealment, the randomization procedure in detail, or whether the analysis followed the assigned groups. It also does not say whether any baseline adjustment was planned or performed. These are not grounds to assume a particular method; they are items that remain unreported in the registry record.

What does the standardized difference add?

The reported pooled standard deviation is 1.358, and the standardized mean difference is -1.399. General statistical explanation: a standardized mean difference puts a contrast in units of a pooled standard deviation rather than in the original score units. It can help compare effects across measures that use different scales, but it does not make the result inherently more meaningful. Here, the direct score-point contrast remains useful because the questionnaire’s scale and direction are described. The registry does not report a prespecified threshold for a meaningful knowledge-score change.

Overall, the posted statistics support a descriptive reading of group averages, variability, an interval estimate, and an unadjusted test. The registry record does not report enough analysis detail to determine whether clustering, baseline measurements, missing outcomes, or multiple outcomes were handled in a particular way.

10. Confidence Intervals and Precision

The point estimate for the online-versus-conventional mean difference is -1.9 knowledge-score points. Its reported confidence interval extends from -2.113 to -1.687. Because the entire reported interval is below zero, the interval is consistent with a lower mean score in the online group than in the conventional group under the analysis used. The confidence level and interval-construction method are not reported in the registry record, so those details cannot be used to further characterize the interval.

General statistical explanation: a confidence interval represents uncertainty in an estimated quantity, not the range of individual participant scores. A narrower interval indicates greater precision under the method’s assumptions, while a wider interval indicates more uncertainty. The interval is not a guarantee that the true difference lies within its limits, and its interpretation depends on the study design and statistical model being appropriate.

The group means are accompanied by standard deviations of 1.53 for conventional education and 1.16 for online education. Those describe observed score spread, while the reported standard errors of the means are 0.087 and 0.066, respectively. These quantities serve different purposes: standard deviations concern variation among participants, and standard errors concern precision of estimates of group means.

Precision of the comparison also depends on design features beyond the number of participants. Since classrooms were randomly assigned, whether the analysis accounted for classroom clustering matters for uncertainty. That information is not reported in the registry record. The record also does not report the confidence level, missing-data handling, or the number of classrooms, limiting a fuller assessment of precision.

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 estimates are participants per arm, not total events. They are illustrations based on the observed effect and assume a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each row considers an effect equal to a stated fraction of the observed effect: 100%, 75%, or 50%. For the 100% planning effect, the estimates are 9 participants per arm for 80% power and 11 participants per arm for 90% power. For 75% of the observed effect, they are 15 and 20 participants per arm. For 50% of the observed effect, they are 33 and 43 participants per arm.

General statistical explanation: power is the probability that a specified statistical procedure will detect an effect of a specified size under its assumptions. The 80% column describes the planned sample size per arm for an analysis with 80% power at the assumed effect size; the 90% column does the same for 90% power. Smaller effects are harder to distinguish from random variation, so planning for smaller effects requires more participants under otherwise similar assumptions.

These figures are planning illustrations, not observed power and not the trial’s original sample-size justification. The original design assumptions and sample-size rationale are not reported in the registry record. The registry’s classroom-level random assignment is also not reflected in the stated planning assumptions, which specify equal allocation and a normal approximation.

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 = -1.900; pooled standard deviation σ = 1.358.
2. n = 2 × (1.96 + 0.842)² × 1.358² / -1.900² = 8.0, rounded up to 9 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 <- -1.9                      # observed difference in means
sigma <- 1.35766343399239                     # 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(5570500)
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 = 9 (80% power), 11 (90% power)
 75% of observed effect: n per arm = 15 (80% power), 20 (90% power)
 50% of observed effect: n per arm = 33 (80% power), 43 (90% power)
power.t.test: 9.1 
Simulated power at n = 9 per arm: 0.794 (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 identifies a primary knowledge outcome and one secondary outcome concerning oral hygiene measures practice. The primary outcome is a score from 0 to 6; the secondary outcome’s detailed measurement and results are not reported in the registry record. The record lists an unadjusted p-value for the primary comparison, but does not report a plan for handling multiple outcomes or multiple statistical tests. It is therefore not possible to determine whether a multiplicity adjustment was planned or used.

General statistical explanation: when several outcomes or comparisons are tested, the chance of at least one apparently notable result can increase. A prespecified hierarchy or adjustment strategy can help manage that issue. The registry record does not report whether such a strategy was specified for this study. The primary result can be described using its reported unadjusted p-value, but it should not be assumed that the result was adjusted for the existence of a secondary outcome.

Missing-data information is also not reported in the registry record. The record does not describe participant flow after assignment, the number with an available primary outcome, reasons for missing scores, or methods for handling missing observations. The group sizes accompanying the result are listed as 312 in each arm, but the record does not explain whether those are all randomized participants or only those included in the outcome analysis.

The analysis population is not reported in the registry record. There is no description of an intention-to-treat analysis, a per-protocol analysis, or any exclusions from the analysis. It is also not reported whether participants were analyzed according to classroom assignment or whether classroom clustering was incorporated in the statistical model. These gaps limit assessment of how closely the posted estimate reflects the randomized design.

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

The posted primary outcome data show a lower average knowledge score in the online group than in the conventional group: 0.81 compared with 2.71 on a scale where higher scores indicate more correct answers. The reported online-versus-conventional mean difference is -1.9, with a confidence interval from -2.113 to -1.687 and an unadjusted p-value of <0.001. These figures describe the observed comparison for the registered primary outcome.

They do not establish why the group averages differ. The registry record does not provide enough detail about classroom-level analysis, missing data, baseline scores, or the exact analysis population to resolve how those features may have affected the estimate. It also does not report the content and delivery details for either education method in enough depth to assess what specific difference between the approaches was evaluated.

The score is a questionnaire-based measure with a possible range from 0 to 6. The record says higher scores are better, but does not give a threshold for a meaningful change or report individual-level score distributions. As a result, the group mean difference should not be translated into a claim about how many children attained a satisfactory score or how much a particular child’s knowledge changed.

The study description mentions questionnaires before and after education, but the posted results do not report baseline means or within-group changes. The reported comparison therefore should not be described as a measured improvement from baseline. Nor should it be taken as evidence about oral hygiene practice: that is listed as a secondary outcome, but its result is not reported in the registry record.

These data are specific to the recorded groups of primary school children in two Egyptian schools. The registry does not report information that would establish how representative those schools or participants are of other settings. The findings are statistical descriptions of the posted outcome, not medical advice and not a basis for a general claim about the effectiveness of either education method.

15. Why This Trial Matters Statistically

This trial illustrates how a randomized comparison can produce a clear numerical contrast while leaving important design and analysis details unspecified in the registry record. The study description reports classroom-level assignment, whereas the posted primary outcome comparison is summarized at the participant level. Whether the analysis accounted for the classroom structure is not reported. This distinction matters because the unit used to assign groups and the unit used in an analysis can affect the uncertainty attached to an estimate.

The endpoint is also instructive because it is a bounded questionnaire score rather than a direct count of clinical events. Its 0-to-6 scale and higher-is-better direction make the mean difference understandable in original units, while the standard deviations and standardized difference provide additional descriptions of variation and scale-relative contrast. These summaries do not show the full distribution of participant scores or how many children reached any prespecified level of knowledge.

Finally, the record demonstrates why statistical interpretation needs both estimates and reporting context. The mean difference, confidence interval, and unadjusted p-value convey the observed comparison and its modeled uncertainty. Information about missing data, outcome analysis populations, multiplicity, classroom adjustment, and the original sample-size rationale is not reported in the registry record. A careful reading keeps the numerical result distinct from unanswered methodological questions, and distinguishes the knowledge endpoint from the listed but unreported practice outcome.

16. 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.

Several trial-specific details needed to assess the result are not reported in the registry record. The study description says classrooms were randomly assigned, but the number of classrooms, randomization procedure, and handling of classroom clustering in the analysis are not stated. The masking entry says single masking without identifying who was masked. Allocation concealment is also not described.

The registry reports pre- and post-education questionnaires, but does not identify whether the displayed group means are post-education values, changes from baseline, or values from another analysis. Baseline group scores and participant flow are not reported with the primary outcome results. Although each group result lists 312 participants, the registry does not explain how these analyzed counts relate to the enrollment entry of 636.

The education methods are named online and conventional, but the specific content, duration, delivery procedures, and fidelity checks are not described in the registry record. Its primary outcome population wording says participants in both arms received an education session through colorful images and cartoons, without clarifying how this relates to the two methods. The questionnaire’s full scoring and validation details are not reported, and no threshold for a meaningful score difference is given.

The confidence level and construction method for the reported confidence interval are not reported. Neither missing-data procedures, analysis population, multiplicity strategy, nor the original sample-size rationale is reported. The secondary practice outcome is named, but its numerical results are not reported in the registry record. These limitations restrict interpretation of the reported comparison and its generalizability.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Comparing the Effect of Online and Conventional Oral Health Education in Egypt — NCT05570500.
• Registry record last updated 2024-01-10; status last verified 2024-01.
• Results first posted 2024-01-10.
• 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.

20. Record Summary

The registry record describes a completed, randomized, parallel-group study of online versus conventional oral health education in primary school children in two schools in Egypt. It lists enrollment of 636, single masking, and Ain Shams University as sponsor. Classrooms in 3rd and 4th grade were randomly assigned according to the study description.

The primary outcome is a 0-to-6 oral health knowledge score at a 2 months timeframe, with higher scores indicating better knowledge. The conventional group mean was 2.71 and the online group mean was 0.81. The reported online-versus-conventional mean difference was -1.9, with a confidence interval from -2.113 to -1.687 and an unadjusted p-value of <0.001.

One secondary practice outcome is listed, but its result is not reported in the registry record. Details about classroom adjustment, missing data, analysis populations, and the original sample-size rationale are also not reported in the registry record.