Question

Antithrombotic drugs are used after coronary stenting to prevent stent thrombosis. A study was performed to compare the efficacy and safety of two antithrombotic drug regimens: Aspirin alone and Aspirin + Ticlopidine. The counts of adverse events are given below in the following table:

Drug Regimen	Number of events	Total subjects administered drug
Aspirin Alone	20	557
Aspirin + Ticlopidine	3	546

Given the results, is there an association between drug regimen and number of adverse events? State the null and alternative hypotheses to answer the research question, report your test statistic and p-value and interpret your results.

Answer 1

H_o:There is no association between drug regimen and number of adverse events

H₁:There is association between drug regimen and number of adverse events.

Let the level of significance be 5%

The test statistic

Drug regimen	Number of events	Total subjects adminstrated drug	Total
Aspirin Alone	20	557	577
Aspirin +Ticlopidine	3	546	549
Total	23	1103	1126

The sample size is 1126

The expected frequencies =

Drug Regimen	Number of events	Total Subjects adminstrated drug	Total
Aspirin Alone			577
Aspirin +Ticlopidine			549
Total	23	1103	1126

The test statistic

  

The critical value of  

We reject Ho

There is no association between drug regimen and number of adverse events