Iranian researchers studied factors affecting patients\' likelihood of wearing o

Question

Iranian researchers studied factors affecting patients' likelihood of wearing orthodontic appliances, noting that orthodontics is perhaps the area of health care with the highest need for patient cooperation. Among their analyses, they compared students in primary school, junior high school, and a high school. The data that follow have almost exactly the same means as they found in their study, but with far smaller samples. The scores for each student is his or her daily hours of wearing the orthodontic appliance.

Primary School: 16,13,18
Junior High School : 8,13,14,12
High School: 20,15,16,18

f) Calculate the appropriate measure of effect size for this sample.

g) Why is it useful to know the effect size in addition to the results of a hypothesis test?

h) How could this study be conducted using a within-group design?

Explanation / Answer

f) In order to compute the effect size, one-way ANOVA is computed. The result is as follows:

Eta-sqaured=SS(Between)/SS(Total)=63.4697/111.6364=0.5685

g. In case of rejection of hypothesis, one might be interested in knowing how large the difference between two means be. According to Cohen, thhe effect size is medium. From the effect size, one conclude therefore, that 56.85% of total variance is accounted for treatment effect.

h. For within group design, the researcher might consider a group primarily and then instead of comparing the group with any other, researcher looks for trends and differences within that group of subjects.

Source of variation SS df MS F Between groups 63.4697 2 31.73485 5.27 Within groups 48.16667 8 6.020833 Total 111.6364 10

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