Formulas
23 statistics and probability formulas explained term by term. Open one and tap each piece to see what it means.
Probability
- Bayes' Theorem Updates the probability of a hypothesis after seeing evidence.
- Conditional Probability The chance of A when you already know B happened.
- Law of Total Probability Adds up the probability of B across every scenario of a partition.
- Binomial Coefficient How many ways there are to choose k items out of n, ignoring order.
- Chebyshev's Theorem A bound on the share of data far from the mean, for any distribution.
Distributions
- Bernoulli Distribution A single trial with two outcomes: success or failure.
- Binomial Distribution The number of successes in n independent trials.
- Poisson Distribution The number of events in an interval, given a mean rate.
- Normal (Gaussian) Distribution The bell curve defined by its mean and standard deviation.
- Central Limit Theorem Why the sample mean tends to a normal distribution as n grows.
Inference
- Z-Score How many standard deviations an observation is from the mean.
- Student's t-Test Compares a sample mean with a hypothesized value when σ is unknown.
- Confidence Interval A range of plausible values for the population mean.
- Chi-Square Test (χ²) Measures the gap between observed and expected frequencies.
Sampling
Association and means
Algebra and calculus
No formula with that name.