A confidence interval for the population mean tells us which values of the mean are plausible (those insie 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 H0: mean = meansub0 starting with a confidence interval: reject Hsub0 if meansub0 is outside the interval and fail to reject it if meansub0 is inside the interval. The alternative hypothesis is always two-sided. Hsuba: mean=meansub0 because the confidence interval extends in both directions from xbar. A 95% confidence interval leads to a test at the 5% significance level because the interval is wron 5% of the time. In general, confidence level C leads to a test at significance leve alpha = 1-C. a medical director found that LDL cholesterol xbar = 124.86 for and SRS of 72 executives. The standard deviation of the LDL of all adults is standard deviation = 40. find the P-value for the z test, to 4 decimal places