Читать книгу Applied Biostatistics for the Health Sciences - Richard J. Rossi - Страница 30

To study whether echinacea is effective in shortening the duration of the common cold, a random sample of 200 volunteers is taken. The 200 subjects are divided into two groups of size 100. Each group gets a supply of 300 mg pills and is instructed to take a 300 mg pill as soon as they recognize cold symptoms and to continue taking a pill each day until their cold symptoms go away. One group will receive 300 mg echinacea pills and the other group 300 mg placebo pills. The subjects are asked to record the duration of each cold they have in the following year.

1 Is this study an experiment or an observational study?

2 What is the target population in this study?

3 What is the response variable in this study?

4 What are the treatments in this study?

5 Is this a prospective or retrospective study?

Solutions

1 This study is an experiment because the researcher assigned the subjects to the treatments.

2 The target population in this study is people having the common cold.

3 The response variable in this study is the duration of the common cold.

4 The treatments in this study are 300 mg echinacea and 300 mg placebo.

5 This is a prospective study because the subjects are being followed forward in time.