Question

PART II.   A study is conducted comparing a new drug to an existing drug on treating hypertension among younger and older adults. DRUG (new v. existing) and AGE CATEGORY (<65 v. 65+) are used as independent variables.  Diastolic blood pressure is the dependent variable.

1. Suppose the researchers reported the following:

Following treatment, average diastolic blood pressure was 84 (±5) mmHg for the <65 year old age group who received the new drug and 90 (±4) mmHg for <65 year old age group who received the existing drug.  Average diastolic blood pressure was 83.5 (±5) mmHg for the 65+ year old age group who received the new drug and 85 (±4) mmHg for 65+ year old age group who received the existing drug.  

Do these results suggest that an interaction is present? If so, why and what type (ordinal or disordinal)?

Answer 1

From the above question,a two way table can be drawn which is shown below

Drug	<65	65+
New	84 (+/- 5)	83.5(+/-5)
Old	90 (+/-4)	85(+/-4)

The results suggest that the interaction is present and the type of interaction is ordinal interaction as the two independent variables (age group and drug) do not intersect with one another .Here the group predicted mean (old drug) is always greater than the mean of new drug.