maths - AS statistics

define population

whole set of items

define census

observes ever member of the population

define sample

selection of items from a population

ADV and DIS of census

ADV = more accurate

DIS = takes longer because every member of the population is asked

ADV and DIS of sample

ADV = quicker + cheaper

DIS = less accurate- may not be representative of the whole population

define random sampling

every member of population has an equal chance of being selected

define systematic sampling

items are chosen at regular intervals from an ordered list (first item selected is chosen at random)

define stratified sampling

population divided into groups (strata) and a sample is taken from each group in proportion to its size

define quota sampling

The population is divided into groups and a set number of individuals is chosen from each group

define opportunity sampling

takes a sample from the people who are available at the time

define discrete data

data that can only take specific, separate values

define continuous data

data that can take any value within a given range