CHAPTER 7 SAMPLING AND SAMPLING DISTRIBUTIONS

parameter

A characteristic of a population.

p chart

A control chart that monitors the proportion of defectives (or some other characteristic) of a production process.

random variable

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

estimate

A particular value of an estimator.

control chart

A plot of statistics of a production process over time. If the statistics randomly fall in an expected range, then the production process is in control. If the statistics reveal an undesirable trend, then adjustment of the production process is likely necessary.

cluster sample

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 sample

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.

Statistical Quality Control

Statistical techniques used to develop and maintain a firm's ability to produce high-quality goods and services.

central limit theorem (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. The approximation steadily improves as the number of observations increases.

standard error

The standard deviation of an estimator.

bias

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

x chart

that monitors the central tendency of a production process.

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. Most statistical methods presume simple random samples.

estimator

A statistic used to estimate a population parameter.

Non-response bias

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

Selection bias

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

expected value

A weighted average of all possible values of a random variable.