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FIGURE A6.1 Minitab Normal Distribution DialogBox
A6.2 MINITABUsing Minitab to Compute NormalProbabilitiesYou can use Minitab instead of Table E.2 to compute nor-mal probabilities. To find the probability that a downloadtime is less than 9 seconds with µ = 7 and σ = 2:
1. Enter 9 in the first row of column C1 of a blankworksheet.
2. Select Calc Probability Distributions Normal.3. In the Normal Distribution dialog box (see Figure A6.1)
select the Cumulative probability option button. Enter7 in the Mean: edit box and 2 in the Standard deviation:edit box. Select the Input column: option button andenter C1 in its edit box. Click the OK button. You willget the output displayed in the top portion of Figure6.19 on page 206.
To find the Z value corresponding to a cumulative areaof 0.10,
1. Enter .10 in row 1 of column C2.2. Select Calc Probability Distributions Normal.3. Select the Inverse cumulative probability option but-
ton. Enter 7 in the Mean: edit box and 2 in the StandardDeviation: edit box.
4. Select the Input Column option button and enter C2in the edit box. Click the OK button.
You will get the output displayed in the bottom portionof Figure 6.19 on page 206.
Using Minitab for a Normal Probability PlotTo construct a normal probability plot in Minitab for the 2003returns of mutual funds, open the MUTUALFUNDS2004.MTW
worksheet. Then,
1. Select Graph Probability Plot.2. In the Probability Plots dialog box, select Single. Click
the OK button.3. In the Probability Plot-Single dialog box (see Figure
A6.2), in the Graph variables: edit box, enter C7 or‘Return 2003’.
FIGURE A6.2 Minitab Probability Plot-Single DialogBox
4. Click the Distribution button. In the Probability Plot -Distribution dialog box (see Figure A6.3), selectNormal in the Distribution drop-down list box. Clickthe OK button to return to the Probability Plot - Singledialog box. Click the OK button.
FIGURE A6.3 Minitab Probability Plot-DistributionDialog Box
BEREMC06_0131536869.QXD 1/24/05 8:10 PM Page 225
226 CHAPTER SIX The Normal Distribution and Other Continuous Distributions
FIGURE A6.4 Minitab Exponential Distribution DialogBox
Using Minitab to Compute ExponentialProbabilitiesTo compute exponential probabilities for the ATM cus-tomer-arrival example using Minitab,
1. Enter .1 in column C1 of a blank worksheet.2. Select Calc � Probability Distributions �
Exponential.3. In the Exponential Distribution dialog box (see Figure
A6.4), select the Cumulative probability option but-ton. In the Scale: edit box, enter .05. This entry is madebecause Minitab defines the mean as the mean timebetween arrivals, 1/λ = 1/20 = 0.05, not the mean num-ber of arrivals, λ = 20. Select the Input column:option button and enter C1 in the Input column: editbox. Click the OK button.
BEREMC06_0131536869.QXD 1/24/05 8:10 PM Page 226