Immediately after the intervention in an experimental study of ...

[CBme]

Immediately after the intervention in an experimental study of the negative effects of smoking tobacco, the state tax on cigarettes increases the cost from 4 to 8 per pack. Which threat to internal validity does this pose?
 
  a. Mortality
  b. History
  c. Testing
  d. Selection

Question 2

What is the essential difference between a control group and a comparison group?
 
  a. A control group's data is collected at the same time as the experimental group's data. A comparison group's data is collected before that of the experimental group.
  b. A control group is larger in size than a comparison group.
  c. A control group exists only is a basic lab situation. All nursing studies use comparison groups.
  d. A control group is randomly assigned. A comparison group is not.

[tandmlomax84]

Answer to Question 1

ANS: B
History is an event that is not related to the planned study but that occurs during the time of the study. History could influence a subject's response to the treatment and alter the outcome of the study. The attrition threat is due to subjects who drop out of a study before completion. The circumstances in which a study is conducted (history) influence the treatment and thus the generalizability of the findings. Sometimes, the effect being measured (testing) can be due to the number of times the subject's responses have been tested. The subject may remember earlier, inaccurate responses and modify them, thus altering the outcome of teh study.

Answer to Question 2

ANS: D
If the study involves an experimental treatment, the design usually calls for a comparison. Outcome measures for individuals who receive the experimental treatment are compared with outcome measures for those who do not receive the experimental treatment. This comparison requires a control groupsubjects who do not receive the experimental treatment. However, in nursing studies, all patients require care, and those who do not receive the study intervention receive standard care. Nurse researchers often refer to the group receiving standard care, but no treatment, as the comparison group rather than the control group. Essentially, the main difference between these terms is that control groups are nearly identical to their experimental groups, except for assignment. Comparison groups differ, because of the time at which data are collected, the way they are constituted, or other circumstances that make them less likely to be nearly identical, leading to a higher occurrence of threats to internal validity.