MS-DS Master of Data science Exploratory Data Analysis 3

Question 1

When computing Pearson correlation between two variables yields r = 0, what can be definitively concluded?

Accepted Answer

There is no linear relationship between the variables

Answer

Pearson r = 0 only rules out a linear association; nonlinear relationships (e.g., quadratic) can still exist with r = 0.

Question 2

Which plot is BEST suited for detecting heteroscedasticity in residuals after fitting a regression model?

Accepted Answer

Residuals vs. fitted values plot

Answer

Plotting residuals against fitted values reveals fan-shaped or patterned spread, which indicates non-constant variance (heteroscedasticity).

Question 3

What is the interquartile range (IQR) used to define in the standard box plot outlier rule?

Accepted Answer

The spread of the middle 50% of data used to set whisker fences

Answer

The standard Tukey rule flags points beyond Q1 − 1.5×IQR or Q3 + 1.5×IQR as outliers, where IQR = Q3 − Q1.

Question 4

A dataset has 10% missing values in a predictor column. To determine whether the missingness is MCAR, MAR, or MNAR, which EDA step is most informative?

Accepted Answer

Comparing distributions of other variables between missing and non-missing groups

Answer

If other variables differ systematically between the missing and observed groups, missingness is likely MAR or MNAR rather than completely random.

Question 5

In a time series EDA, a plot of autocorrelation function (ACF) shows significant spikes at lags 12, 24, and 36. What pattern does this indicate?

Accepted Answer

Annual seasonality (period = 12)

Answer

Significant ACF spikes at multiples of 12 in monthly data indicate a recurring annual seasonal pattern.

MS-DS Master of Data science Practice Test

MS-DS Master of Data science Practice Test

MS-DS Master of Data science Exploratory Data Analysis 3