Applied Statistics Chapter 7
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.
cluster sample
formed when the population is divided into groups (clusters) based on geographic areas
stratified random sample
formed when the population is divided into groups (strata) based on one or more classification criteria
statistical quality control
statistical techniques used to develop and maintain a firm's ability to produce high-quality goods and services
standard error
the standard deviation of an estimator
bias
the tendency of a sample statistic to systematically overestimate or underestimate a population parameter
statistic
A calculated numerical value (such as the sample mean) that characterizes some aspect of a sample set of data, and that is often meant to estimate the true value of a corresponding parameter (such as the population mean) in an underlying population; any function of a number of random variables, usually identically distributed, that may be used to estimate a population parameter
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.
parameter
A quantity or statistical measure that, for a given population is fixed and that is used as the value of a variable in some general distribution or frequency function to make it descriptive of that population: the mean and variance of a population are population parameters
simple random sample
A sample of n observations that has the same probability of being selected as any other sample of n observations. Most statistical methods presume simple random samples
random variable
a function that assigns numerical values to the outcomes of an experiment
estimate
a particular value of an estimator
estimator
a statistic used to estimate a population parameter
nonresponse 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