R Programming Language Certification Statistical Analysis & Modeling 2 — Questions and Answers
Question 1: Which family argument in glm() is used for logistic regression?
- gaussian
- poisson
- binomial (Correct answer)
- gamma
Correct answer: binomial
Logistic regression models binary outcomes using glm() with family=binomial, which applies the logit link function by default.
Question 2: What does the confint() function compute for a fitted model in R?
- Confidence intervals for model coefficients (Correct answer)
- Prediction intervals for new data
- AIC and BIC values
- Variance inflation factors
Correct answer: Confidence intervals for model coefficients
confint() returns confidence intervals for the parameters of a fitted model, defaulting to 95% confidence level.
Question 3: Which test should you use to compare variances between two groups in R?
- t.test()
- var.test() (Correct answer)
- bartlett.test()
- levene.test()
Correct answer: var.test()
var.test() performs an F-test to compare the variances of two groups and determines if they are statistically equal.
Question 4: What does AIC stand for in model selection?
- Average Information Criterion
- Akaike Information Criterion (Correct answer)
- Adjusted Index of Correlation
- Analytic Information Coefficient
Correct answer: Akaike Information Criterion
AIC (Akaike Information Criterion) penalizes model complexity to balance goodness of fit with parsimony; lower AIC indicates a better model.
Question 5: Which R function performs a Wilcoxon rank-sum test (non-parametric equivalent of t-test)?
- wilcox.test() (Correct answer)
- mann.whitney()
- ranksum()
- nonpar.test()
Correct answer: wilcox.test()
wilcox.test() performs both the Wilcoxon signed-rank test (one-sample/paired) and the Wilcoxon rank-sum (Mann-Whitney) test for two independent samples.
Question 6: What does the predict() function do when called on a fitted lm() model?
- Retrains the model on new data
- Generates predicted values for new or existing data (Correct answer)
- Plots model residuals
- Computes cross-validation scores
Correct answer: Generates predicted values for new or existing data
predict() uses the fitted model coefficients to generate predicted (fitted) values for the original data or new observations supplied via newdata.
R Programming Language Certification Statistical Analysis & Modeling 2
Which family argument in glm() is used for logistic regression?