statistical significance Flashcards
what is the difference between populations and samples
populations are an entire group of people (e.g., offenders, victims, specific culture)
impossible to test entire population, so we rely on samples drawn from population
what is random sampling?
everyone in population has equal chance of being selected
simple random - randomly picked from list of names
systematic - every nth person from random starting point
multistage - select institution randomly, then select PPs from there
what is stratified random sampling
can help with representativeness
random sampling, but with constraints according to characteristics of population of interest
stratified sampling - select randomly from people sorted into particular characteristics
disproportionate sampling - selecting from more underrepresented groups
cluster sample - random samples from specific geographical area
what is non random sampling
more common
quota - people fit researcher defined categories
convenience - people selected because they are easy to recruit
snowball - other PPs suggest similar people
purposive - selected because they are of interest to the research
theoretical sampling - collecting additional PPs as theory develops
what is the alternative/experimental hypothesis?
prediction of what we think will happen
what is the null hypothesis?
flip side of alternative hypothesis - prediction of no effect (no correlation)
what is a p value? - very important for exam
indicates the probability of observing results as more extreme than obtained if the null hypothesis is true
does NOT indicate the probability of the null hypothesis being true
what is a type 1 error?
chance of concluding there is an effect, when there really isn’t
what is a type 2 error?
chance of concluding there isn’t an effect, when there really is
what can control type 1 and type 2 errors
bigger sample sizes
good experimental design
consider using lower p value
