306 Chapter 7 The Normal Distribution MINITAB Finding areas under a normal curve The following procedure computes the area to the left of a given value. Step 1. Click Calc, then Probability Distributions, then Normal. Step 2. Select the Cumulative probability option. Step 3. Enter the value for the mean in the Mean field and the value for the standard deviation in the Standard deviation field. Step 4. To compute the area to the left of a given x, enter the value for x in the Input constant field. Step 5. Click OK. Figure E Figure E illustrates finding the area to the left of x = 280 with �� = 272 and �� = 9. To find the area to the right of x = 280, subtract this result from 1 (Example 7.13). Finding a normal value corresponding to a given area The following procedure is used to calculate a normal value corresponding to an area to the left. Step 1. Click Calc, then Probability Distributions, then Normal. Step 2. Select the Inverse Cumulative Probability option. Step 3. Enter the value for the mean in the Mean field and the value for the standard deviation in the Standard deviation field. Step 4. Enter the area to the left of the desired normal value and click OK. Figure F Figure F illustrates finding the normal value that has an area of 0.98 to its left, where �� = 100 and �� = 15 (Example 7.17). EXCEL Finding areas under a normal curve The following procedure computes the area to the left of a given value. Step 1. In an empty cell, select the Insert Function icon and highlight Statistical in the category field. Step 2. Click on the NORM.DIST function and press OK. Step 3. To compute the area to the left of a given x, enter the value of x in the X field. Step 4. Enter the value for the mean in the Mean field and the value for the standard deviation in the Standard deviation field. Step 5. Enter TRUE in the Cumulative field and click OK. Figure G Figure G illustrates finding the area to the right of x = 280 with �� = 272 and �� = 9 by subtracting the area on the left from 1 (Example 7.13).
navidi_monk_elementary_statistics_2e_ch7-9
To see the actual publication please follow the link above