Plea provide answers for part A and B

a. A researcher collects a sample of 18 measurements from a Normally distributed population and wishes to find a 99% confidence interval for the population mean. What value should he use for t'? b. If he instead decides to use a 95% confidence interval, will the interval be wider or be narrower or stay the same? Why? Click the icon to view the t-table. a. To find a 99% confidence interval for the population mean, he should use for t". (Round to three decimal places as needed.)