Miscellaneous

Question 1

Key Concept

Answer 1

• The independent variable is the one that the experimenter is manipulating, and the dependent variable is the one that is being observed.
• On a graph the independent variable belongs on the x-axis and the dependent variable belongs on the y-axis

Question 2

Cohort Studies

Answer 2

• Type of observational study
• Cohort studies are those in which subjects are sorted into groups based on differences in risk factors (exposure), and then assessed at various intervals to determine how many subjects in each group had a certain outcome.
• For example, a study in which 100 smokers and 100 nonsmokers are followed for 20 years while counting the number of subjects who develop lung cancer in each group would be an example of a cohort study.

Question 3

Cross-Sectional Studies

Answer 3

• Type of observational study
• Cross-sectional studies attempt to categorize patients into different groups at a single point in time.
• For example, a study to determine the prevalence of lung cancer in smokers and nonsmokers at a given point in time would be an example of a cross-sectional study.

Question 4

Case-Control Studies

Answer 4

• Type of observational study
• Case-control studies start by identifying the number of subjects with or without a particular outcome, and then look backwards to assess how many subjects in each group had exposure to a particular risk factor.
• For example, a study in which 100 patients with lung cancer and 100 patients without lung cancer are assessed for their smoking history would be an example of a case-control study.

Question 5

Bias and Confounding

Answer 5

• Bias is a result of flaws in the data collection phase of an experimental or observational study.
• Confounding is an error during analysis.

Question 6

Selection Bias

Answer 6

• The most prevalent type of bias
• The subjects used for the study are not representative of the target population.

Question 7

Detection Bias

Answer 7

• Detection bias results from educated professionals using their knowledge in an inconstistent way.
• For example, high blood pressure and diabetes mellitus are more common in the obese population; thus, a physician may screen obese patients for hypertension and diabetes at a higher rate than healthy-weight patients, inflating the true value of the secondary measurement.

Question 8

Hawthorne Effect or Observation Bias

Answer 8

• The Hawthorne effect, or observation bias, posits that the behavior of study participants is altered simply because they recognize that they are being studied.

Question 9

Confounding

Answer 9

• Confounding is a data analysis error.
• The data may or may not be flawed, but an incorrect relationship is characterized.
• “Third-party” variables are called confounding variables

Question 10

Internal Validity and External Validity

Answer 10

• Internal validity refers to the identification of causality in a study between the independent and dependent variables.
• External validity refers to the ability of a study to be generalized to the population that it describes.