Research cht 6

population

the total people(social units) the researcher wishes to generalize (apply the findings)

Sample

a subset of the population (some but not all elements in the population)

• those responding to the study

Representatives

typical of the group

• what characteristics vary among people?

• aggregate characteristics

• one of the hardest things to do

Sampling

the process of selecting observations from a population

biased sampling

sample is biased when it does not fully represent the larger population from which it was selected (eg, rate my professor)

Probability sampling

sampling is biased when the cases have unequal or unknown chances of being selected

random sampling

all cases have an equal chance of being selected for inclusion in a study

sampling frame

the set of all cases from which the sample actually selected

simple random sample (SRS)

every possible subject and combinations of subjects from your target population has an equal chance of being included in the study

• equal chance!

sampling error

the amount that a sample mean deviate from the true population mean

systematic sample approach

1.) select a random starting point

2.) then select every kth item thereafter until your sample of desired size is collected

stratified sampling approach

1.) break population down into catergories (strata)

2.) then select a random sample of sample of cases from each strata

cluster sampling

• means group of similar things posistioned in proximity

Three step process:

a.) break the population down into categories

b.) then randomly sample of clusters

c.) select (sammple) all cases within each randomly select cluster

eg: often used in polling research; eg:predict election outcomes (before and on election day)