Free EPPP Test Research Methods and Statistics Questions and Answers — Questions and Answers
Question 1: A researcher conducts an experiment in a highly controlled laboratory setting to investigate the effect of a specific memory-enhancing drug on recall. Participants are randomly assigned to either a placebo or drug condition. While the results show a significant effect, a primary concern with this type of study is its potential for limited:
- Internal validity
- External validity (Correct answer)
- Construct validity
- Statistical conclusion validity
Correct answer: External validity
External validity refers to the extent to which the results of a study can be generalized to other settings, other people, and over time. Highly controlled laboratory experiments, while excellent for establishing cause-and-effect (high internal validity), may create an artificial environment that does not reflect real-world conditions, thus limiting the generalizability, or external validity, of the findings.
Question 2: A research team is planning a study to test the efficacy of a new therapeutic intervention. They are concerned about failing to detect an effect that actually exists. Which of the following is the most direct and common way to increase the statistical power of their study?
- Decrease the alpha level (e.g., from .05 to .01)
- Use a quasi-experimental design
- Increase the sample size (Correct answer)
- Decrease the effect size
Correct answer: Increase the sample size
Statistical power is the probability of correctly rejecting a false null hypothesis, or the ability to detect a true effect. The most common and direct way to increase statistical power is to increase the sample size. A larger sample provides a more accurate estimate of the population parameter, reducing sampling error and making it more likely that a true effect will be detected.
Question 3: In a study on patient satisfaction, participants are asked to rate their experience with a clinic on a scale from 1 (Very Dissatisfied) to 5 (Very Satisfied). This type of data is measured on which scale of measurement?
- Nominal
- Interval
- Ratio
- Ordinal (Correct answer)
Correct answer: Ordinal
An ordinal scale is used when data can be ranked or ordered, but the intervals between the ranks are not necessarily equal. In this scenario, we know that a rating of 4 is better than 3, but we cannot assume that the difference in satisfaction between a 1 and 2 is identical to the difference between a 4 and 5. Therefore, it is an ordinal scale.
Question 4: A school psychologist wants to evaluate the effectiveness of a new anti-bullying program. The program is implemented in one middle school, and the psychologist compares the number of reported bullying incidents in that school to the number of incidents in a neighboring middle school that does not have the program. What type of research design is being used?
- True experimental design
- Quasi-experimental design (Correct answer)
- Correlational design
- Longitudinal design
Correct answer: Quasi-experimental design
This is a quasi-experimental design because it compares groups but lacks random assignment. The participants (the students in the schools) were in pre-existing groups and were not randomly assigned to the condition with the program or the condition without it. This lack of randomization is the key feature that distinguishes a quasi-experiment from a true experiment.
Question 5: A researcher wants to compare the effectiveness of three different types of therapy (CBT, Psychodynamic, and Humanistic) on reducing symptoms of depression. After the intervention, each group's mean score on the Beck Depression Inventory (BDI) is calculated. Which statistical test would be most appropriate to determine if there is a significant difference among the three group means?
- Independent samples t-test
- Chi-square test
- Analysis of Variance (ANOVA) (Correct answer)
- Pearson correlation coefficient
Correct answer: Analysis of Variance (ANOVA)
Analysis of Variance (ANOVA) is the appropriate statistical test for comparing the means of three or more independent groups. An independent samples t-test is only suitable for comparing the means of two groups. Using multiple t-tests would inflate the probability of making a Type I error. A chi-square test is for categorical data, and a Pearson correlation is for examining the relationship between two continuous variables.
Question 6: A pharmaceutical company conducts a large clinical trial for a new antidepressant. Their analysis concludes that the drug is not significantly more effective than a placebo. However, a later meta-analysis of several studies reveals that the drug does, in fact, have a small but clinically meaningful effect. The original study's conclusion is an example of a:
- Type I error
- Type II error (Correct answer)
- Placebo effect
- Sampling bias
Correct answer: Type II error
A Type II error occurs when a researcher fails to reject a null hypothesis that is actually false. In this scenario, the null hypothesis was that there is no difference between the drug and the placebo. The study failed to reject this hypothesis (concluding no effect), when in reality an effect existed. This is also known as a 'false negative.'
Free EPPP Test Research Methods and Statistics Questions and Answers
A researcher conducts an experiment in a highly controlled laboratory setting to investigate the effect of a specific memory-enhancing drug on recall.
Participants are randomly assigned to either a placebo or drug condition.
While the results show a significant effect, a primary concern with this type of study is its potential for limited: