MS-DS Master of Data science Research & Data Analysis 3

Question 1

A researcher collects data from volunteers who self-select into a study. The primary threat to external validity is:

Accepted Answer

Self-selection bias

Answer

Self-selection bias occurs when participants who volunteer differ systematically from the target population, limiting generalizability.

Question 2

When comparing more than two group means simultaneously, a one-way ANOVA is preferred over multiple t-tests because:

Accepted Answer

Multiple t-tests inflate the Type I error rate

Answer

Running multiple t-tests increases the familywise error rate; ANOVA controls it by testing all groups in a single analysis.

Question 3

A confusion matrix for a binary classifier shows TP=80, FP=10, FN=20, TN=90. What is the precision?

Accepted Answer

0.89

Answer

Precision = TP / (TP + FP) = 80 / (80 + 10) = 80/90 ≈ 0.889.

Question 4

In principal component analysis (PCA), the first principal component is defined as:

Accepted Answer

The linear combination of variables that explains the most variance

Answer

PC1 is the direction (linear combination) in the feature space along which the projected data has maximum variance.

Question 5

A dataset contains 5% missing values that are Missing Not at Random (MNAR). The best imputation strategy is:

Accepted Answer

Multiple imputation with auxiliary variables explaining missingness

Answer

MNAR requires modeling the missingness mechanism; multiple imputation with variables that predict missing data reduces bias compared to simpler methods.

MS-DS Master of Data science Practice Test

MS-DS Master of Data science Practice Test

MS-DS Master of Data science Research & Data Analysis 3