The following exercise is a "what-if" analysis designed to determine what happens to the test statistics and interval estimates when elements of the statistical inference change. You may need to use the appropriate appendix table to answer this question. (a) A statistics practitioner drew a random sample of 380 observations and found that I = 680 and s = 100. Estimate the population mean with 90% confidence. (Round your answers to two decimal places.) lower bound upper bound (b) Repeat part (a) with a 95% confidence level. (Round your answers to two decimal places.) lower bound upper bound (c) Repeat part (a) with a 99% confidence level. (Round your answers to two decimal places.) lower bound upper bound (d) What is the effect on the confidence interval estimate of increasing the confidence level? The width of the interval widens as the confidence level increases