Question

Treatment for depression: Researchers conducted a study of 18 patients whose depression had not responded to treatment (Zarate, 2006). Half received one intravenous dose of ketamine, hypothesized quick fix for depression; half received one intravenous dose of placebo. Far more of the patients who received ketamine improved, as measured by the Hamilton Depression Rating Scale, usually in less than 2 hours, than patients on placebo.

a.What is the population of interest, and what is the sample in the study?

b. Was random selection likely used? Explain your answer.

c. Was random assignment likely used? Explain your answer.

d. What is the independent variable and what are the levels? What is the dependent variable?

e. What is the null hypothesis and what is the research hypothesis?

f. What decision did the researchers make? (Respond using the language of inferential statistics.)

g. If the researchers were incorrect in their decision, what kind of error did they make? Explain your answer. What are the consequences of this type of error, both in general and in the situation?

Answer 1

The researchers in the above experiment conducted a study on patients with depression who did not respond to treatment priory. The population of interest is patients with depression and the sample is chosen from the population. Population is the number of people in total in a geographical area from which the sample is chosen. The researcher wanted to study the effect of a drug and placebo on individuals with depression. The total number of people suffering from depression are hypothetically 200 in number. The experimenter chose 18 people. He would choose a sample from the population which would best represent it the best. A sample (any number of people) is collected from the population for the purpose of administering different drugs to see it's effect on depression. A sample is considered to be the representation of the population. These individuals who are called samples, are assigned to different treatment groups.

From the population, the sample was randomly chosen and thus, the sample size includes 18 people. Half of the sample which means, 9 people were assigned to the experimental group who were introduced to the drug, ketamine. The other half was randomly assigned to the control group.

The independent variable here is the drug. It has has been manipulated in two ways, thus, there are two levels, ketamine and placebo. The dependent variable is patients with depression. The independent variable is manipulated to see its effects on the dependent variable.