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A Confidence Interval for the mean weight (in pounds) of grizzly bears in Jellystone National Park is: 330 < μ < 442 a. What was the mean weight (in pounds) of bears in the sample? b. What is the margin of error (in pounds) in this confidence interval? Submit Question
In this problem, we explore how to find what are called critical values. These are Z values that have a given "middle" area. Consider the graph shown below. Suppose that you want to find the Z values so that the red shaded area is 0.67. Z We will use - Ze to represent the Z value at the left of the shaded area and Zc to represent the Z value at the right. To find Ze, we must use the invNorm command on a calculator. But that command requires that we enter a "left" area. So we need to find the area of the "left" tail. Since the red area is 0.67, and the total area under the curve is 1, the remaining white area (both tails) must be 1-0.67 - So in the graph above, the white area on the left (the "left tail") must be Thus the area to the left of Ze, the red area plus the white left tail area, is Thus on a TI calculator we have: Zeinvnorm( Submit Question ,0,1) In ClassCalc, it would be Ze NormalDist(0, 1). inversecdf(answer) B And so Ze, rounded to two decimals, is: