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Annotated Output | Post Hoc Comparisons

Computer Output

The tables of statistics can be used to determine the inferential statistics.

Summary Statistics for the Data
             N       M      SD    Skew    Kurt
Level1   4.000   2.000   2.449   0.544  -2.944
Level2   4.000   6.000   2.449   0.544  -2.944
Level3   4.000   7.000   2.449  -0.544  -2.944

The values of the group statistics are calculated separately for each group or condition. They are not identical to the values obtained from analyzing the variable as a whole.

The tables of inferential statistics show the key elements to be calculated.

Confidence Intervals for the Posthoc Mean Differences
                   Diff      SE      df      LL      UL
Level1 v Level2   4.000   1.732   9.000  -0.836   8.836
Level1 v Level3   5.000   1.732   9.000   0.164   9.836
Level2 v Level3   1.000   1.732   9.000  -3.836   5.836

Hypothesis Tests for the Posthoc Mean Differences
                   Diff      SE      df       t       p
Level1 v Level2   4.000   1.732   9.000   2.309   0.106
Level1 v Level3   5.000   1.732   9.000   2.887   0.043
Level2 v Level3   1.000   1.732   9.000   0.577   0.835

Confidence Intervals for the Posthoc Standardized Mean Differencens
                      d      SE      LL      UL
Level1 v Level2   1.633   0.943  -0.215   3.481
Level1 v Level3   2.041   1.007   0.068   4.015
Level2 v Level3   0.408   0.825  -1.209   2.025

For the 1 vs. 2 comparison, HSD = 2.309 and p = .106. This would not be considered a statistically significant diffeence.

For the 1 vs. 3 comparison, HSD = 2.887 and p = .043. This would be considered a statistically significant difference.

For the 2 vs. 3 comparison, HSD = 0.577 and p = .835. This would not be considered a statistically significant difference.

For each comparison, the researcher estimates the true population mean difference adjusted for multiple comparisons (knowing that the estimates could be incorrect).

For the 1 vs. 2 comparison, the 95% CI is [-0.836, 8.836].

For the 1 vs. 3 comparison, the 95% CI is [0.164, 9.836].

For the 2 vs. 3 comparison, the 95% CI is [-3.836, 5.836].

Cohen’s d for each comparison can be calculated but is not shown here.

APA Style

Post hoc tests build on the ANOVA results and provide a more focused comparison among the groups and usually follows a presentation of the ANOVA (which already includes the descriptive information).

A series of Tukey’s HSD comparisons revealed that the first group (n = 3, M = 2.00, SD = 2.45) scored substantially and significantly lower Outcome scores than the third group (n = 3, M = 7.00, SD = 2.45), 95% CI [0.16, 9.84], t(9) = 2.89, p = 043. However, the other comparisons revealed effectively little and not significant differences between the other groups (ps > .05).

Alternatively, the means, standard deviations, and confidence intervals could be presented in a table or figure associated with this text.