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For Questions 12-17: A researcher is interested in treatment of infants with plagiocephaly. He enrolled 100 infants with plagiocephaly and randomized them to one of three groups: Group 1 – Received...

For Questions 12-17: A researcher is interested in treatment of infants with plagiocephaly. He enrolled 100 infants with plagiocephaly and randomized them to one of three groups:

Group 1 – Received standard care (helmeting at 4 months)

Group 2 – Received weekly parent education sessions focused on tummy time and safe sleep

Group 3 – Received soft tissue manual therapy by an occupational therapist

The researcher evaluated the success of the interventions by measuring transcranial diameter difference (TDD) at 6 months. The researcher tested the assumptions of normality and homogeneity of variances and both assumptions were met. Here is the SPSS output:

 Descriptives TDD N Mean Std. Deviation Std. Error 95% Confidence Interval for Mean Minimum Maximum Lower Bound Upper Bound 1.00 33 .6788 .22327 .03887 .5996 .7580 .20 1.00 2.00 33 .4667 .29545 .05143 .3619 .5714 .00 .90 3.00 34 .6471 .19107 .03277 .5804 .7137 .20 .90 Total 100 .5980 .25544 .02554 .5473 .6487 .00 1.00
 ANOVA TDD Sum of Squares df Mean Square F Sig. Between Groups .866 2 .433 7.513 .001 Within Groups 5.593 97 .058 Total 6.460 99

Post Hoc Tests

 Multiple Comparisons Dependent Variable: TDD Tukey HSD (I) Treatment (J) Treatment Mean Difference (I-J) Std. Error Sig. 95% Confidence Interval Lower Bound Upper Bound 1.00 2.00 .21212* .05912 .002 .0714 .3528 3.00 .03173 .05868 .851 -.1079 .1714 2.00 1.00 -.21212* .05912 .002 -.3528 -.0714 3.00 -.18039* .05868 .008 -.3201 -.0407 3.00 1.00 -.03173 .05868 .851 -.1714 .1079 2.00 .18039* .05868 .008 .0407 .3201 *. The mean difference is significant at the 0.05 level.

1. The SPSS output above shows that the researcher ran an ANOVA. Why would the researcher chose to run an ANOVA instead of running multiple t-tests to compare the three groups? (5 points)

2. What is the null hypothesis being tested? (5 points)

3. What is the F value from this analysis? (5 points)

4. What is the p value from the ANOVA analysis? (5 points)

5. Would you reject or fail to reject the null hypothesis? (5 points)

6. Using both the ANOVA output table and the Multiple Comparisons post hoc table, what conclusion would you make? (10 points)

Solution

David answered on Dec 27 2021
1. The SPSS output above shows that the researcher ran an ANOVA. Why would the
esearcher chose to run an ANOVA instead of running multiple t-tests to compare the
three groups? (5 points)
For comparing means between 3 or more groups one way ANOVA is used. To test
which pair differs significantly I use Post Hoc analysis (turkey crammer test).
Running multiple t test to compare 3 groups is not easy and comfortable. Running...
SOLUTION.PDF