Simple Random
Equal chance of choosing
random number generator
numbers from a hat
Convenience
Choosing the easiest people = not representative of the population
friends
first 10 people you see
Systematic
Random starting point, using a fixed interval
every 3rd student on a class register
Quota
Sample sizes in proportion to who you’re polling
School is 55% girls, 45% boys => sample should have the same percentage
Stratified
Splitting into smaller groups
boys and girls