stastistical sampling Flashcards
what are the 6 sampling methods?
stratified
systematic
quota
random
cluster
opportunity
what is a population
the entirety of what your testing
what is a sample
a small section (subset) of the population
what is a census
survey on the entire population
✅ and ❌ of a census
✅ accurate results
❌ time consuming
expensive
test items must remain intact
✅ and ❌ of a sample
✅ quicker
easier
❌ bias - unrepresentative
why might sampling methods be unsatisfactory?
sample size is too small
sample is unrepresentative
biased
what is a sampling unit
each individual from a sampling list
what is a sampling frame
a list of sample units
named or numbered
cluster sampling
when population is separated into clusters and random clusters are sampled
✅ and ❌ of cluster sampling
✅ cheaper
Larger samples
Quick
❌ bias
stratified sampling
population divided into groups and random samples taken from each group to fill calculated categories
✅ and ❌ of stratified sampling
✅ random
representative
❌ time consuming
need a sampling frame- unit
random sampling
picking at random so each member has an equal chance
✅ and ❌ of random sampling
✅ no bias
❌ unrepresentative
time consuming for large population
opportunity sampling
picking units that are easiest to reach
✅ and ❌ of opportunity sampling
✅ easy
quick
❌ bias - unrepresentative
quota sampling
population is split into groups and units selected till quotas (calculated group to represent) are filled
✅ and ❌ of quota sampling
✅ representative
❌ bias
systematic sampling
choosing at intervals - nth terms
✅ and ❌ of systematic sampling
✅ quick
easy
❌ must have a list to avoid bias
what is the equation to work out category sizes for stratified sampling?
size of sample/size of population x no of units within a group= category size
