data handling notes

Sampling and bias

• sample data must be representative
• the population is the whole group you want to find out about
• often you can't survey the whole population
• a sample is a small group from the population
• for a sample to be representative it needs to be: a random sample (every member has an equal chance of being in it) and big enough for the size of the population
• to spot bias you need to think about when, where and how the sample is taken and how many members are in it
• if certain groups are excluded, the sample isn't random and that can lead to bias from things like age, gender and different interests
• if the sample is too small, it's also likely to be biased

Sampling methods

random sampling

• assign a number to every member of the population
• create a list of random numbers
• match the random numbers to members of the population

stratified sampling

• find the proportion…