Question

For the following cases, suggest the most appropriate statistical method for the research question and provide the reasons from the following:

One sample z-test, One sample t-test, Two independent samples t-test, Paired t-test

The objective of a study by van Vollenhoven et al. was to examine the effectiveness of Etanercept alone and Etanercept in combination with methotrexate in the treatment of rheumatoid arthritis. They performed a retrospective study using data from the STURE database, which collects efficacy and safety data for all patients starting biological treatments at the major hospitals in Stockholm, Sweden. The researcher identified 40 subjects who were prescribed Etanercept only and 57 who were given Etanercept with methotrexate. One of the outcome measures was the number of swollen joints. Is there sufficient evidence at α = 0.05 level of significance for us to conclude that there is a difference in mean swollen joint counts in the relevant populations?

Answer 1

Most appropriate statistical method for the given research question is two independent samples t test.

Reasons for selecting two independent samples t test are

(A) We have two different samples, first sample with 40 subjects and second sample with 57 subjects.

(B) Both samples undergo different treatment conditions

(C) Samples are randomly selected and independent.

So, two independent samples t test is most appropriate statistical testing for the given data.

it is neither one sample z test nor one sample t test because data consist of two independent samples, so there is no chance of using one sample z test or one sample t test.

Paired t test is not useful because the data is not paired, i.e. two samples include different data items.