The mean has a lower standard error. The sampling distribution of the mean centers over the population mean better than other distributions such as the mode or median. The standard error for the sample mean is lower than other sample statistics. Confidence Interval, specifies a range of values in which the parameter lies. The degree to which the estimate is trusted is called the confidence coefficient.
Confidence Intervals are always two tailed.
When sample size is increased, the estimate of the standard error is decreased and the confidence interval is more precise. So, the confidence interval is larger. This test is used when the population mean and standard deviation are known. Training improves Learning. Learning operationalizes to GRE performance.