Coding Grandmaster · project 29 of 46 · premium, free for now

Do two things move together?

Write correlation(xs, ys) that returns Pearson's r rounded to 4 decimal places. Print it for study hours against marks.

Learn

Correlation measures how closely two lists move together. Pearson's r runs from −1 (one rises exactly as the other falls) through 0 (no straight-line link) to +1 (a perfect rise together). It is the sum of the products of each pair's distances from their means, divided by the product of the two spreads. A strong correlation never proves one thing causes the other.

Your task

Write correlation(xs, ys) that returns Pearson's r rounded to 4 decimal places. Print it for study hours against marks.

Stretch challenge

Find two lists with correlation near 0 that still have a clear curved pattern.

← A histogram in text Scaling and z-scores →

Python

Press Run to see what your program prints.

Keep going in Coding Grandmaster

Averages

Write mean(data), median(data) and mode(data). If several values tie for most common, mode returns the smallest of them. Print all three for the list.

Start →26

How spread out?

Write data_range(data), variance(data) and std_dev(data) (population versions, dividing by n). Print them for the data, rounding the standard deviation to 4 decimal places.

Start →27

Quartiles and outliers

Write quartiles(data) returning (q1, q2, q3) by the method above, and outliers(data) returning the sorted list of outliers by the 1.5 × IQR rule.

Start →28

A histogram in text

Count how many students got each grade and print one line per grade in alphabetical order, like A | #### 4.

Start →30

Scaling and z-scores

Write min_max(values) and z_scores(values) (use the population standard deviation). Both return lists with each number rounded to 2 decimal places.

Start →

Practise the idea

⚙️ Play Function Machine

Feed numbers into a mystery machine, plot what comes out, then crack its secret rule.

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