chapter 6: estimation procedures for sample means and proportions

point estimate

an estimate of a population value where a single value is specified

margin of error

aka sampling error or margin of sampling error; radius (half the size) of a confidence interval for a sample mean or proportion

bias

a criterion used to select sample statistics as estimators; a statistic is unbiased if the mean of its sampling distribution is equal to the population value of interest

efficiency

the extent to which the sample outcomes are clustered around the mean of the sampling distribution

alpha

the probability of error or the probability that a confidence interval does not contain the population value; alpha levels are usually set at 0.10, 0.05, 0.01, or 0.001

confidence level

a frequently used alternative way of expressing alpha, the probability that an interval estaimte that does not contain the population value; confidence levels of 90%, 95%, 99%, and 99.9% correspond to alphas of 0.10, 0.05, 0.01, and 0.001 respectively

90% confidence level

±1.65

95% confidence level

±1.96

99% confidence level

±2.58

99.9% confidence level

±3.29

student’s t distribution

a distribution used in the construction of confidence intervals when the population standard deviation is unknown

error bar

a graphic display device used to illustrate the confidence interval of a sample statistic