Four randomly selected data values have been sampled from a population that is normally distributed. 12.72 21.38 9.4 13.87 Round all final numerical answers to 3 decimal places, where necessary. a) Compute the mean and standard deviation of the 4 randomly selected values. mean = ___ standard deviation = ____ b) Determine if a z or t value should be to compute the level of confidence for your sample. After selecting "A" or "B", enter the critical value that corresponds to a 95% confidence interval. A. z = ____ B. t = ___ c) Compute the margin of error for a 95% confidence interval. The question will be graded based on parts a and b. Error = ____ d) Using your answers above, construct a 95% confidence interval for the population mean. You will receive no credit if these values are not used. Remember to write the smaller value first, then the larger value. This question will be graded based on previous parts of this question. (__, ___)