2. A specified range is based on an estimate of a population characteristic calculated from a random sample. The probability that the range contains the true population value is the
A. Error rate.
B. Lower precision limit.
C. Confidence level.
D. Standard error of the mean.
ANSWER (C) is correct.
REQUIRED: The probability that an estimate based on a random sample falls within a specified range.
DISCUSSION: In principle, given repeated sampling and a normally distributed population, the confidence level is the percentage of all the precision intervals that may be constructed from simple random samples that will include the population value. In practice, the confidence level is regarded as the probability that a precision interval calculated from a simple random sample drawn from a normally distributed population will contain the population value.
Answer (A) is incorrect. The error rate in an attribute a sampling application is the proportion of incorrect items in a population.
Answer (B) is incorrect. The lower precision limit is the lower bound of the interval constructed from the sample result at a specified confidence level.
Answer (D) is incorrect. The standard error of the mean is the standard deviation of the distribution of sample means.