What would happen to the confidence interval if you wanted to be 95 percent certain of it? You would have to draw the limits (ends) of the intervals closer to the tails, in order to encompass an area of 0.95 between them instead of 0.90. You are 90 percent certain that the true population mean of football player weights is between 192 and 204 pounds.
#Confidence interval in minitab express 2 samples plus
Another way to express the confidence interval is as the point estimate plus or minus a margin of error in this case, it is 198 ± 6 pounds.
A confidence interval is usually expressed by two values enclosed by parentheses, as in (192, 204). The weight values for the lower and upper ends of the confidence interval are 192 and 204 (see Figure 1). You can determine the weights that correspond to these z‐scores using the following formula: You can define that area by looking up in Table 2 (in "Statistics Tables") the z-scores that correspond to probabilities of 0.05 in either end of the distribution. This question is the same as asking what weight values correspond to the upper and lower limits of an area of 90 percent in the center of the distribution. What is a 90 percent confidence interval for the population weight, if you presume the players' weights are normally distributed? Assume that the population standard deviation is σ = 11.50. The mean weight of the sample of players is 198, so that number is your point estimate. You are able to select ten players at random and weigh them. Suppose that you want to find out the average weight of all players on the football team at Landers College.