CHAPTER 12: ESTIMATION Key 'Ierms Point estimate -- a single value that represents some unknown population characteristic, such as the population mean. Confidence interval A range of values that, with a known degree of certainty, includes an unknown population characteristic, such as a population mean. Level of confidence The percent of time that a series of confidence intervals includes the unknown characteristic, such as the population mean. Margin of error That which is added to and subtracted from some sample value, such as the sample proportion or sample mean, to obtain the limits of a confidence interval. "Itaxt Review A researcher may wish to estimate the value of a population mean rather than test a hypothesis based on a population mean. Estimation is possible with use of (1) and (2) . A point estimate is a single value that represents some unknown (3) characteristic. The problem with point estimates is that they tend to be (4) because of (5) . Therefore, the researcher uses a more accurate type of estimate, (6) . A confidence interval is a range of values that, with a known degree of certainty, includes an unknown population characteristic, such as (7)