Revision GuideStatistics & Data
Statistics Revision Guide
A fuller printable guide to descriptive statistics, centre measures, spread measures, and interpretation habits that help prevent misleading summaries.
Printable PDFOpen download
Quick Reference SheetStatistics & Data
Probability and Counting Methods Cheat Sheet
A fuller cheat sheet for combinations, permutations, and binomial-style reasoning, built around order, constraints, and event definition.
Filename: probability-and-counting-methods-cheat-sheet.pdfFile size: 3 KB
Formula highlights
Combinations
nCr = n! / (r!(n - r)!)
Binomial probability
P(X = k) = nCk x p^k x (1 - p)^(n - k)
Choose the model
- Order matters -> permutations
- Order does not matter -> combinations
- Repeated yes/no trials with fixed probability -> binomial thinking
Formula highlights
- nPr = n! / (n - r)!
- nCr = n! / (r!(n - r)!)
- Binomial probabilities require clear event definition and model assumptions
Worked examples
Committee selection uses combinations.
Role assignment uses permutations.
At least one success is often easiest through the complement event.
Quick checks
- State what counts as success before calculating.
- Check whether the trials are independent enough for a binomial model.
- Remember that large factorial-based answers are normal.
Related calculators
Use the formulas in live tools.
Combinations Calculator
Use the Combinations Calculator to calculate combinations from your own dataset with practical output and sensible validation.
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Permutations Calculator
Use the Permutations Calculator to calculate permutations from your own dataset with practical output and sensible validation.
Statistics & DataOpen
Binomial Probability Calculator
Use the Binomial Probability Calculator to calculate binomial probability from your own dataset with practical output and sensible validation.
Statistics & DataOpen
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