Data Science with Python Certification Data Science with Python (Basic) 5

Question 1

In a list comprehension [x**2 for x in range(5) if x % 2 == 0], how many elements does the result contain?

Accepted Answer

3

Answer

range(5) produces 0,1,2,3,4; filtering by x%2==0 keeps 0,2,4 — three values — so the result has 3 elements: [0,4,16].

Question 2

Which measure of central tendency is most robust to outliers?

Accepted Answer

Median

Answer

The median (middle value) is resistant to outliers because it depends on rank order, not the actual extreme values.

Question 3

What does np.where(condition, x, y) return?

Accepted Answer

An array with x where condition is True and y where it is False

Answer

np.where(condition, x, y) returns an array selecting elements from x when condition is True and from y when it is False.

Question 4

Which pandas dtype is assigned to a column containing text strings by default?

Accepted Answer

object

Answer

pandas stores text (string) data as the 'object' dtype by default, though a dedicated StringDtype is also available.

Question 5

What is the primary purpose of cross-validation in machine learning?

Accepted Answer

To estimate how well a model generalizes to unseen data without wasting samples

Answer

Cross-validation rotates which portion of data is used for validation, giving a more reliable generalization estimate than a single train/test split.

Data Science with Python Certification Practice Test