Final answer:
The sample mean (x-bar) is used to estimate the population mean (µ). It is combined with the standard error to reflect the variability in the estimation. The 90th percentile for the sample mean provides insights into user engagement.The correct option is e. x-bar
Step-by-step explanation:
The statistic used to estimate the population mean is e. x-bar which is the sample mean. In statistics, the sample mean is used as the point estimate for the population mean when the population mean (µ) is unknown. When inferring about a population mean based on a sample statistic, we often use the sample mean (x-bar) along with measures like the standard error to indicate the uncertainty or variability expected in the estimate.
The standard error of the mean is a vital concept as it helps determine how far the sample mean might be from the true population mean. In the question's provided context, if a sample mean time for app engagement is given, we can estimate the 90th percentile for the sample mean, which reflects a time below which 90 percent of the sample falls. This would provide insight into standard user engagement times.