A confidence interval for the population mean / tells us which values of # are plausible (those inside the interval) and which values are not plausible (those outside the interval) at the chosen level of confidence. You can use this idea to carry out a test of any null hypothesis Ho: # - #o starting with a confidence interval: reject Ho if Ho is outside the interval and fail to reject if Ho is inside the interval. The alternative hypothesis is always two-sided, Ha: # # #o because the confidence interval extends in both directions from x, A 95% confidence interval leads to a test at the 5% significance level because the interval is wrong 5% of the time. In general, confidence level C leads to a test at significance level a = 1 - C. A medical director found the LDL cholesterol x = 124.86 for an SRS of 72 executives. The standard deviation of the LDL of all adults is o = 40. Give a 90% confidence interval for the mean LDL # of all executives in this company, assuming that the standard deviation is the same as for all adults. Give your answer as an interval in the form (*, *): Give your numbers to two decimal places. 90% confidence interval: 117.71 Incorrect