ch 7

Parameter

numerical summary of a population

Central Limit Theory CLT

The CLT states that the sum or mean of a large number of independent observations from the same underlying distribution has an approximate normal distribution.

Population

The complete collection of items of interest in a statistical problem.

selection bias

A systematic underrepresentation of certain groups from consideration for a sample.

finite population correction factor (FPC)

A correction factor that accounts for the added precision gained by sampling a larger percentage of the population. It is implemented when the sample constitutes at least 5% of the population.

point estimator

A function of the random sample used to make inferences about the value of an unknown population parameter

random variable

A function that assigns numerical values to the outcomes of an experiment.

cluster sampling

A population is first divided up into mutually exclusive and collectively exhaustive groups of observations, called clusters. A cluster sample includes observations from randomly selected clusters

stratified random sampling

A population is first divided up into mutually exclusive and collectively exhaustive groups, called strata. A stratified sample includes randomly selected observations from each stratum. The number of observations per stratum is proportional to the stratum's size in the population. The data for each stratum are eventually pooled.

Sample statistic

A random variable used to estimate the unknown population parameter of interest.

simple random sample

A sample of n observations that has the same probability of being selected from the population as any other sample of n observations.

estimator

A statistic used to estimate a population parameter

Sample

A subset of a population of interest.

Socially-desirability bias

A systematic difference between a group's "socially acceptable" responses to a survey or poll and this group's ultimate choice.

nonresponse bias

A systematic difference in preferences between respondents and nonrespondents of a survey or a poll.

bias

The tendency of a sample statistic to systematically overestimate or underestimate a population parameter.

control chart

a plot of statistics of a a production process over time