Formulas and rules
Every key math formula and rule, organised by topic and school level, with examples and study tips.
Statistics 5
Mean
mean = sum of values / number of values
The mean averages the data.
Median, mode and range
Median is the middle value when ordered. Mode is the most frequent. Range is highest minus lowest.
Probability
P = favourable outcomes / total outcomes
Probability runs from 0 (impossible) to 1 (certain).
Combined probability
independent: P(A and B) = P(A) x P(B)
For independent events, multiply the probabilities.
Quartiles and spread
IQR = Q3 - Q1
Quartiles split ordered data into four parts; the IQR measures spread.