a sample selected so that each item or person in the population has the same chance of being included
systematic random sample
a random starting point is selected, and then every kth member of the population is selected
stratified random sample
a population is divided into subcatagories, called strat, and a sample is randomly selected from each stratum
cluster sample
a population is dvided into clusters using naturally occuring geographic or other boundaries. then clusters are randomly selected and a sample is collected by randomly selecting from each cluster
sampling error
the diff between a sample statistic and its corresponding population parameter
sampling distribution of the sample mean
a probability distribution of all possible sample meant of a given size
central limit theorem
if all samples of a particular size are selected from any population, teh sampling distribution of the sample mean is approximately a normal distribution. this approximation improves with larger samples
point estimate
the statistic, computed from sample information which is used to estimate the population paremeter
confidence interval
a range of values constructed from a sample data so that the population parameter is likely to occur within that range at a specified probability. the specified probability is called the level of convidence