# A-level Mathematics/OCR/S1/Discrete Random Variables

## Derived statistics[edit]

SYLABUS EXTRACT:

Understand, use and interpret different measures of central tendency (mean, median, mode) and variation (range, interquartile range, standard deviation), e.g. in comparing and contrasting sets of data; Calculation of the mean and standard deviation of a set of data (including grouped data) either from the data itself or from given n totals such as Σx and Σx2 , or Σ(x−a) and Σ(x−a)2 .

## Discrete random variables[edit]

SYLABUS EXTRACT:

(a) construct a probability distribution table relating to a given situation involving a discrete random variable X, and calculate the expectation, variance and standard deviation of X (the notations E(X ) for expectation (also referred to as expected value or mean) and Var(X ) for variance, are included); (b) use formulae for probabilities for the binomial and geometric distributions, and model given situations by one of these, as appropriate (the notations B(n, p) and Geo( p) are included); (c) use tables of cumulative binomial probabilities (or equivalent calculator functions); (d) use formulae for the expectation and variance of the binomial distribution, and for the expectation of the geometric distribution.