PRC Statistical Analysis & Software 3 — Questions and Answers
Question 1: A researcher uses listwise deletion to handle missing data. What is the primary risk of this approach?
- It inflates the sample size artificially
- It can introduce bias if data are not missing completely at random (Correct answer)
- It always underestimates variance
- It requires normally distributed variables
Correct answer: It can introduce bias if data are not missing completely at random
Listwise deletion can produce biased estimates when missingness is related to observed or unobserved variables (MAR or MNAR mechanisms).
Question 2: Which SAS procedure is used to run a multiple linear regression?
- PROC FREQ
- PROC MEANS
- PROC REG (Correct answer)
- PROC UNIVARIATE
Correct answer: PROC REG
PROC REG in SAS performs ordinary least squares regression, including multiple regression with several predictors.
Question 3: Cronbach's alpha is a measure of:
- Test-retest reliability
- Internal consistency reliability (Correct answer)
- Inter-rater reliability
- Predictive validity
Correct answer: Internal consistency reliability
Cronbach's alpha quantifies how consistently items on a scale measure the same underlying construct (internal consistency).
Question 4: In a 2×2 factorial ANOVA, an interaction effect means:
- Both main effects are non-significant
- The effect of one factor depends on the level of the other factor (Correct answer)
- Sample sizes in all cells are equal
- The dependent variable violates normality
Correct answer: The effect of one factor depends on the level of the other factor
An interaction indicates that the relationship between one independent variable and the outcome differs across levels of the second independent variable.
Question 5: Which Python library is most commonly used for statistical modeling and hypothesis testing in research?
- NumPy
- Matplotlib
- SciPy/statsmodels (Correct answer)
- Seaborn
Correct answer: SciPy/statsmodels
SciPy and statsmodels provide a broad range of statistical tests, regression models, and inferential statistics tools for Python-based research.
Question 6: A Q-Q plot in which points fall closely along the diagonal reference line suggests:
- Significant skewness
- The data approximate a normal distribution (Correct answer)
- Heteroscedasticity in residuals
- Multicollinearity among predictors
Correct answer: The data approximate a normal distribution
When observed quantiles align with theoretical normal quantiles on a Q-Q plot, the data are approximately normally distributed.
Question 7: When conducting a chi-square test of independence, what does a significant result indicate?
- The variables have a causal relationship
- The observed and expected cell frequencies differ more than chance alone explains (Correct answer)
- The association is strong enough to be practically meaningful
- Both variables are normally distributed
Correct answer: The observed and expected cell frequencies differ more than chance alone explains
A significant chi-square indicates that the distribution of one categorical variable differs across levels of another beyond what chance predicts, suggesting an association.
PRC Statistical Analysis & Software 3
A researcher uses listwise deletion to handle missing data.
What is the primary risk of this approach?