Box Plots and Quartiles: Five-Number Summary and Outliers
How to find quartiles and the interquartile range, draw a box-and-whisker plot, and spot outliers with the 1.5 × IQR rule.
Statistics & Probability
10 guides.
Confidence Intervals Explained (Without the Jargon)
What a 95% confidence interval really means, how to calculate one from a sample mean, and how sample size changes the margin of error.
Line of Best Fit: Linear Regression and Correlation Explained
How to find the least-squares line of best fit, what the correlation coefficient r and r² mean, and why correlation is not causation.
Probability Basics: And, Or, Not and Dice
Learn the basic probability rules for 'and', 'or' and 'not', independent and mutually exclusive events, and how to count dice outcomes.
The Binomial Distribution Explained Step by Step
When to use the binomial distribution, the formula for exactly k successes, at-most and at-least probabilities, and the mean and standard deviation.
The Poisson Distribution Explained with Examples
When to use the Poisson distribution, how to calculate P(X = k) from an average rate λ, and how it compares with the binomial distribution.
How to Calculate Mean, Median and Mode
Find the mean, median, mode and range of a data set step by step, learn which average to use, and see how outliers affect each one.
Permutations vs Combinations: When Order Matters
Learn the difference between permutations and combinations, the nPr and nCr formulas, and how to use them for lotteries, teams and passwords.
Standard Deviation and Variance Explained Step by Step
What standard deviation measures, how to calculate it for a population or a sample, why samples divide by n − 1, and a full worked example.
The Normal Distribution and Z-Scores Made Simple
Understand the bell curve, the 68–95–99.7 rule, z-scores and how to find normal probabilities, with worked examples on test scores and heights.