Statistics: practice, test and prove it

Covers averages, spread, distributions, sampling, correlation, hypothesis tests and confidence intervals.

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Start the statistics test Read the first lesson

Statistics screenings mix small calculations with interpretation. You may be asked to find a median from six numbers, work out a standard deviation, or say what a p-value of 0.03 does and does not mean. Wrong answers usually come from misreading a definition rather than from hard arithmetic.

Every calculation on this page uses small numbers you can check with a pencil. The lessons explain how to describe data with averages and spread, and how to read hypothesis tests and confidence intervals without the common misinterpretations.

Benchmark: The pass mark on this site is 80%, and statistics is commonly screened for data analyst, research, quality and junior data science roles. Requirements vary by employer.

Lessons

Describing data: averages, spread and distributionsWhen to use mean, median or mode, how to calculate standard deviation by hand, and what the normal distribution tells you.Lesson 1

Hypothesis tests, p-values and confidence intervalsHow to read p-values correctly, the two error types, how sample size affects precision, and why correlation is not causation.Lesson 2

Probability basics and sampling: the rules behind every test questionHow to combine probabilities with AND and OR, work out conditional probability from a table, and recognise biased samples.Lesson 3

Correlation coefficient and simple regression by handHow to calculate Pearson r from a small dataset, read its sign and size, and fit and interpret a straight-line prediction.Lesson 4

Interview prep

Statistics interview questionsStatistics questions interviewers commonly ask analysts, with answers that explain the reasoning rather than only the definition.6 questions

Certificate

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Common questions

Can I use a calculator during statistics screenings?

Many screenings allow one, but questions are usually designed with small numbers. Practising by hand helps you spot a wrong answer quickly.

Do I need to memorise statistical tables?

No. It is enough to know a few landmarks, such as 1.96 for a 95% confidence interval and the 68, 95 and 99.7 percent rule for the normal distribution.

Is this the same as the statistics in a data science course?

It covers the foundations those courses build on. Machine learning topics such as model evaluation are tested separately on this site.

Statistics test for interviewWhat the screening round looks like, with a 5-question sample.