StatisticsdrillStatistics that sticks, with new numbers every time.
Practice the statistics behind reports, surveys and A/B tests. Every attempt brings a fresh sample. Check your answer, see the worked steps and the spreadsheet function that does it for you.
Read it, solve it, see why.
- 01Read a real scenarioTicket times, survey shares, conversion rates and sales data, the numbers analysts see at work.
- 02Enter one numberUse a calculator, a spreadsheet or a pencil. For tests, also choose reject or fail to reject.
- 03Learn from the checkSample or population, one tail or two, z or t. Hints and the worked answer follow.
New numbers, every attempt. Each of the 53 problem types is a template, not a fixed question. Press New numbers and you get a new sample, a new table or a new test, so you learn the method, not the answer.
Five levels, from the mean to A/B tests.
| 01 | Describing data | Mean, median, mode and range, sample vs population standard deviation, z-scores, percentiles with a stated method, the coefficient of variation and weighted means. |
| 02 | Probability | Complements, the addition and multiplication rules, conditional probability from a two-way table, Bayes with a screening test, total probability, expected value and counting. |
| 03 | Distributions | Binomial exactly k and at least k, Poisson, normal areas and percentile cutoffs, the sampling distribution of the mean and the normal approximation. |
| 04 | Inference | t and z intervals, required sample size, one-sample and paired t tests, two-proportion z tests and chi-square tests of independence, with a reject or fail to reject decision. |
| 05 | Relationships | Correlation, covariance, regression slope and intercept, predictions and residuals, R squared, reading a slope in units, and A/B test lift and significance. |
Timed mode for real speed.Each problem gets a clock. Hints and answers stay locked until time is up, and your best times are kept.
Start free. Pay once you are hooked.
Pro
- Probability, distributions, inference and regression
- Worked solutions with Excel and Google Sheets functions
- Progress and best times saved to your account
Payments open soon. The free exercises work now.
Questions
Who is this for?
Business, analytics and social science students, and working analysts who use statistics in reports, dashboards and experiments. If you want to get quick and reliable at the calculations behind the software, this is for you.
What does new numbers every time mean?
Each problem type is a template. Every attempt generates a fresh sample or a fresh scenario, so you practice the method instead of memorizing an answer. New numbers gives you another version of the same problem whenever you like.
How are answers checked?
Each question states how to round. Answers within one and a half units of the last stated decimal count, and whole numbers such as sample sizes must match exactly. For hypothesis tests you also choose reject or fail to reject, and both parts are checked. When an answer is off, the checker names the likely mistake: population instead of sample standard deviation, one tail instead of two, z instead of t, an unpooled standard error, a complement, a percent entered as a decimal, or rounding too early.
Do I need statistical software?
No. A calculator is enough for most problems, and a spreadsheet helps for the rest. Every worked solution shows the formula with the numbers filled in, the steps, and the matching Excel or Google Sheets function, such as STDEV.S, NORM.DIST, T.DIST.2T, CHISQ.DIST.RT or SLOPE.
Can I see the data?
Yes. Show the data opens the generated sample as a small table, with a histogram, a scatter plot or a shaded normal curve where it helps.
Do I need an account?
No. The first five problem types work without one and save progress in your browser. A free account keeps progress across devices, and Pro unlocks the rest.
How do I cancel the monthly plan?
Open Account and choose Cancel subscription. That is the whole process: you keep Pro until the end of the period you paid for and are not charged again. If Pro is not for you, you get a full refund within 14 days of paying.
What if my answer is right but marked wrong?
Answers are checked on the result they produce, not on how they are written, so any correct answer passes. If a check still gets it wrong, use the report link under the result. Reports are reviewed, and a check that is wrong gets fixed.