You're Betterat StatisticsThan You Think.
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How learning actually happens inside Sigma.
Four steps. One loop. You'll feel the rhythm by the second question.
A real problem — no hand-holding yet.
Each session opens with a question drawn from your current difficulty tier. You see the full problem, nothing more.
A researcher observes the following counts in four categories: 18, 22, 24, 16. Under the null hypothesis of equal proportions, what is the expected count per cell?
The reasoning, before the answer.
One tap opens a plain-language explanation of the concept — with a hand-drawn diagram. You learn the why first.
Under the null hypothesis of equal proportions, what is the expected count per cell?
The idea: If all categories are equally likely, you'd split the total evenly. Total = 18 + 22 + 24 + 16 = 80. Divided by 4 cells = 20.0 per cell.
Expected = Total ÷ Number of categories
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Feb 17 – Feb 23
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Everything you need — from first week to quals.
540+ scaffolded questions across 18 topics, organized by the difficulty tiers your coursework actually uses.
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10 questions across descriptive stats, probability, and inference. No sign-up required. See where you stand in under 8 minutes.
A dataset has values: 4, 7, 7, 9, 13. What is the median?
Hint: The median is the middle value when data is sorted in order. With 5 values, the 3rd value is the middle.