The nurse is conducting a study on how regular physical activity ...

[rachel9]

The nurse is conducting a study on how regular physical activity affects the risk for developing lung cancer among smokers.
 
  One group leads a sedentary lifestyle whereas the other has agreed to undergo regular supervised exercise in the gym of a local hospital. During the study, the sole treadmill in the gym broke down and was unable to be used for the last half of the study. Several study participants who preferred the treadmill to other machines did not exercise as long or as intensely as they might otherwise have. Which threat to the external validity of the study does this represent?
  A) Interaction of history and intervention
  B) Interaction of selection and intervention
  C) Experimenter/participant effect
  D) Novelty

Question 2

The nurse is conducting a study that will consider how heart clients respond to various interventions following a heart attack. The nurse is concerned about the threat that testing could pose to the internal validity of the study.
 
  How might testing affect the study?
  A) The long commute that a subject must take to a testing center as part of the study might change the subject's response to an intervention.
  B) One subject develops an unrelated anemia, which causes fatigue, which in turn affects the outcome of the study.
  C) Multiple measurements of participants' cortisol levels could cause stress in the participants and thus influence their cortisol levels, thereby altering the outcome of the study.
  D) Mistakes are made when a number of subjects who should have been assigned to one intervention group are assigned to another, which may affect the outcome of the study.

[kkenney]

Answer to Question 1

Ans: A
Feedback:
Interaction of history and intervention occurs when the circumstances of the study influence the results of the study, decreasing the generalizability of the findings. Such is the case with the broken treadmill that potentially decreased the participant's overall exercise volume. Interaction of selection and intervention occurs when subjects willing to participate in the study are not representative of the target population, thus limiting the generalizability of the results. Experimenter/participant effect occurs when the researcher has preconceived expectations of the intervention, resulting in bias and affecting the generalizability of the findings. Novelty occurs when a new intervention affects the outcome of the study because of either enthusiasm or skepticism by the researchers or the participants.

Answer to Question 2

Ans: C
Feedback:
Testing is the effect of multiple measurements of participants' responses that could influence the participants' responses, thereby altering the outcome of the study. History is events that are occurring during the study, which could influence participants' responses to the intervention. Maturation is unplanned and unrecognized changes in the participants that could affect the findings of the study, such as fatigue, hunger, or increased knowledge. Selection is the process by which participants are selected and grouped for a study. This threat is more likely to occur when randomization is not possible.

[rachel9]

Excellent

[aliotak]

TYSM