Studied by 4 people
Definitions of sampling and their methids, as given by the aqa board Large Data set key facts listed by TLMaths
Simple Random Definition
Every possible sample (of a given size) has an equal chance of being selected
Simple Random method
Assign number to each member of the population
Use a random number generator to generate n numbers, limiting the numbers it can generate from 1 - n. Skip and repull for any numbers that are pulled twice. Once n numbers have been generated, re assign the numbers back to the associated member of the population
Stratified Definition
splitting population into groups relevant to research, then random sampling from each group in proportion to the size of the group
Stratified method
Identify groups to split the population to
Calculate how many of each group shoukd be included, (group/population size * sample size wanted)
Conduct random sample to find sample size wanted in each group
Opportunity Definition
Selecting sample based on convenience and availability
Opportunity Adv
does not find random sample#
may produce good estimate of population parameters
cheap
convenient
may not be generalisable
Stratified Adv
srs is representative of overall population, but strat equalizes frequency
requires list of entire population
determining which factors are relevanty to research not always obvious
random
Simple random Adv
requires list of entire population
may be hard to get responses from generated numbers
time consuming and expensive
random and unbiased
Systematic Definition
Taking participants at regular intervals
Systematic Method
Give each name a number from 1 - n
calculate how often a number needs to be selected (population/sample size wanted) = x
Randomly select a number between 1 and x and select every x person on the register from the first person selected
Systematic Adv
avoids unwanted clustering
if there was a fault every x sample, the systematic may end up clustering/fail
practically easier than number generators
random
less random than srs as no longer independent
requires list of entire population
Quota Defintion
Splitting population into groups relevant to research, then selecting participants from those groups using opportunity sampling
Quota Adv
cheap
easy
convenient
alternative to strat when list of population not available
ensures samples relevant to factors identified
NOT RANDOM
Cluster Definition
Splits population into groups bases on convenience (eg location) called clusters, the randomly choosing which group to study further
Cluster Adv
RANDOM
least random out of random methods
worse than strat, high chance of choosing unrepresentative sample
significantly cheaper than alternatives
does not require list of entire population
Note
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