Quiz: Foundations

Time for a test. Ten questions on data skills. Pause, commit to an answer, and keep your own score.

• Ten questions
• Pause and commit
• Keep score

Question 1

Question 1. What should you do first with any new table? A, Train a model. B, Check its shape and what one row means. C, Make a dashboard. D, Delete outliers. Pause the video and choose. The answer is B. Knowing what a row means is the most important fact.

Question 2

Question 2. Your mean is well above your median. What's likely? A, A long tail to the right. B, No outliers. C, A perfect bell curve. D, An error. Pause the video and choose. The answer is A. A few large values pull the mean up.

Question 3

Question 3. After a left join, you have more rows than before. Why? A, Duplicate keys on the right. B, Missing values. C, The index reset. D, Nothing is wrong. Pause the video and choose. The answer is A. Each duplicate multiplies your rows, so count before and after.

Question 4

Question 4. What's the safest way to fill missing incomes? A, The median, with a flag. B, Zero. C, The maximum. D, Random text. Pause the video and choose. The answer is A. The median resists outliers, and the flag records what you did.

Question 5

Question 5. What does WHERE do that HAVING doesn't? A, Filters before grouping. B, Sorts rows. C, Joins tables. D, Limits rows. Pause the video and choose. The answer is A. HAVING filters the groups afterward.

Question 6

Question 6. Which SQL finds the top product in each city? A, ROW_NUMBER with PARTITION BY. B, ORDER BY only. C, DISTINCT. D, UNION. Pause the video and choose. The answer is A. It's the classic interview pattern.

Question 7

Question 7. Why compare with the same day last week? A, It removes weekday effects. B, It is faster. C, It adds data. D, It removes outliers. Pause the video and choose. The answer is A. Compare like with like.

Question 8

Question 8. What's a good chart title? A, Sales by city. B, Two cafes need attention. C, Figure one. D, Data. Pause the video and choose. The answer is B. The title should state the conclusion.

Question 9

Question 9. What's the top quarter of customers usually worth? A, A quarter of revenue. B, A large share of value. C, Nothing. D, Exactly half. Pause the video and choose. The answer is B. Value is concentrated in most businesses.

Question 10

Question 10. An insight that changes no decision is worth what? A, Everything. B, Very little. C, A bonus. D, It depends on the chart. Pause the video and choose. The answer is B. The goal is a better decision.

Summary