Data Science Analysis 2

Question 1

A dataset of household incomes has a mean far higher than its median. What does this indicate?

Accepted Answer

Right (positive) skew

Answer

When the mean exceeds the median, a long right tail of high values pulls the mean up, indicating positive skew.

Question 2

Which measure of central tendency is most robust to outliers?

Accepted Answer

Median

Answer

The median depends only on the middle value(s) and is unaffected by extreme observations.

Question 3

You compute the interquartile range (IQR) to detect outliers. Which boundary commonly flags an outlier?

Accepted Answer

Below Q1 - 1.5*IQR or above Q3 + 1.5*IQR

Answer

The standard Tukey rule flags points beyond 1.5*IQR past the first or third quartile.

Question 4

A correlation coefficient between two variables is -0.9. What does this describe?

Accepted Answer

A strong negative linear relationship

Answer

A value near -1 indicates a strong inverse linear association.

Question 5

Which statement about correlation and causation is correct?

Accepted Answer

Correlation does not imply causation

Answer

Two variables can correlate due to confounders or coincidence without any causal link.

Data Science Practice Test