6-5 Assessing Normality 299 Normal Quantile Plots Access tech supplements, videos, and data sets at www.TriolaStats.com TECH CENTER Statdisk 1. Click Data in the top menu. 2. Select Normal Quantile Plot from the dropdown menu. 3. Select the desired data column and click Plot. TIP: Select Normality Assessment in the dropdown menu under Data to obtain the normal quantile plot along with other results helpful in assessing normality. StatCrunch StatCrunch generates a QQ Plot that is similar to the normal quantile plot and can be interpreted using the same criteria given in this section. 1. Click Graph in the top menu. 2. Select QQ Plot in the dropdown menu. 3. Select the desired data column. 4. Click Compute! Minitab Minitab generates a probability plot that is similar to the normal quantile plot and can be interpreted using the same criteria given in this section. Probability Plot 1. Click Stat in the top menu. 2. Select Basic Statistics from the dropdown menu and select Normality Test from the submenu. 3. Select the desired column in the Variable box and click OK. Probability Plot with Boundaries 1. Click Graph in the top menu. 2. Select Probability Plot from the dropdown menu, select Single,and click OK. 3. Select the desired column in the Graph variables box and click OK. 4. If the points all lie within the boundaries, conclude that the data are normally distributed. If points are outside the boundaries, conclude that the data are not normally distributed. R R command: qqnorm(x) TIP: The R command qqline(x) can be used to add a reference line. A complete list of R statistical commands is available at TriolaStats.com Excel XLSTAT Add-In (Required) 1. Click on the XLSTAT tab in the Ribbon and then click Describing Data. 2. Select Normality tests from the dropdown menu. 3. Enter the desired data range in the Data box. If the first row of data contains a label, check the Sample labels box. 4. Click the Charts tab and confirm that the Normal Q-Q plots box is checked. 5. Click OK and scroll down the results to view the Normal Q-Q plot. TI-83, 83 84 Plus Calculator 8 us Ca cu ato 1. Open the STAT PLOTS menu by pressing F, E. 2. Press [ to access the Plot 1 settings screen as shown: a. Select ON and press [. b. Select last graph type, press [. c. Enter name of list containing data. d. For Data Axis select X. 3. Press B then 9 (ZoomStat) to generate the normal quantile plot. 4. Press A to customize graph and then press D to view the normal quantile plot.
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