The following sample of n = 7 scores was obtained from a population with unknown parameters. Scores: 2, 18, 15, 5, 15, 8, 7. a. Compute the sample mean and variance. (Note: These are descriptive values that summarize the sample data.) b. Compute the estimated standard error for M. (Note: This is an inferential value that describes how accurately the sample mean represents the unknown population mean.)