Question

From Statistics and Data Analysis from Elementary to Intermediate by Tamhane and Dunlop, pg 290. Tell in each of the following instances whether the study uses an independent samples or a matched pairs design.

a) Two computing algorithms are compared in terms of the CPU times required to do the same six test problems.

b) A survey is conducted of teens from inner city schools and suburban schools to compare the proportion who have tried drugs.

c) A psychologist measures the response times of subjects under two stimuli; each subject is observed under both the stimuli in a random order.

d) An agronomist compares the yields of two varieties of soybean by planting each variety in 10 separate plots of land (a total of 20 plots).

Answer 1

A study design is a strategy employed while carrying out a particular study or experiment. A study that involves two groups, can be either a paired-samples design or an independent samples design. A paired samples design or a matched pair design is when the two groups in the study are matched or paired i.e. both the groups are basically the same but are just subjected to two different scenarios or conditions. An independent samples design is the one where the two samples are randomly selected and are independent of each other.

a) There are two algorithms under consideration. Both algorithms are subjected to the same six tests. Since the two algorithms are independent of each other, the study is an independent sample design.

b) There are two groups of teens. One that belongs to inner-city schools while the other belongs to suburban schools. The individuals in the two groups are independent of each other and hence the study design is independent samples.

c) The study involves certain subjects and two conditions. The same subjects are checked for both the conditions but in random order. Hence, the subjects in one group are the same as the subjects in the other group. Therefore, this is a matched sample study.

d) There are two varieties of soyaean that are being checked. A sample from each variety is plotted on 10 different plots. Since the samples in each group are unique, they are independent of each other. Therefore, the study design is independent samples design.