Chapter 4 - Designing Studies Flashcards
collects data from every individual in the population
census
statistical study of the entire group of individuals we want information about
population
subset of individuals in the population from which we actually collect data
sample
- state exactly what population we want to describe
- state exactly what we want to measure
sample survey
choosing individuals from the population who are easy to reach results in a ____.
-often produces unrepresentative data & is bias
convenience sample
using a method that favors some outcomes over others
bias
if you’re asked to describe how the design of a study leads to bias, you’re expected to do two things:
1) identify a problem with the design
2) explain how this problem would lead to an underestimate or overestimate
another term for voluntary response samples
self selected samples
- consists of people who choose themselves by responding to a general invitation
- people who feel strongly about an issue
- most responders share same opinion leading to bias
voluntary response sample
usually not representative of a larger population of interest
-uses a chance process to determine which members of a population are included in the sample
ex- pulling names out of a hat
random sampling
-resulting sample of a random sampling method
-size n is chosen in a way which every group of n individuals in the population has an equal chance to be selected as the sample
ex- drawing 20 slips out of a hat containing 200 identical slips
simple random sample (srs)
stratified random sample and strata
- classifying population into groups of similar individuals (strata)
- choosing separate SRS in each stratum and combine these SRSs to form the sample
- works best when the individuals in each stratum are similar with respect to what is being measured
cluster sample
- classify the population into groups of individuals that are located near each other (clusters)
- choose an SRS of the clusters
list of individuals from which a sample will be drawn
sampling frame
bad sampling methods
convenience sampling or voluntary response
occurs when some members of the population cannot be chosen in a sample;
ex- a sample survey of households will not account for homeless people
under coverage
- occurs when an individuals chosen for the sample can’t be contacted or refuses to participate
- can only occur after sample has been selected
non response