Distribution Analyses |

To view or change the options associated with your distribution analysis, click on the **Output** button from the variables dialog. This displays the output options dialog.

**Figure 38.4:** Distribution Output Options Dialog

The options you set in this dialog determine which tables and graphs appear in the distribution window. A distribution analysis can include descriptive statistics, graphs, density estimates, and cumulative distribution function estimates. By default, SAS/INSIGHT software displays a moments table, a quantiles tables, a box plot, and a histogram. Individual tables and graphs are described following this section.

You can specify the coefficient in the **Parameters:Alpha:** entry field. The confidence level is used in the basic confidence intervals and the trimmed/Winsorized means tables. You can specify in the **Parameters: Mu0:** entry field. is used in the tests for location and the trimmed/Winsorized means tables. You can also specify in the **Parameters: Theta:** entry field. The parameter is used in the parametric density estimation and cumulative distribution for lognormal, exponential, and Weibull distributions.

If you select a **Weight** variable, tables of weighted moments, weighted quantiles, weighted confidence intervals, weighted tests for location, and weighted frequency counts can be generated. Robust measures of scale, tests for normality, and trimmed/Winsorized means are not computed. Graphs of weighted box plot, weighted histogram, and weighted normal QQ plot can also be generated.

The **Trimmed/Winsorized Means** button enables you to view or change the options associated with trimmed and Winsorized means. Click on **Trimmed/Winsorized Means** to display the **Trimmed/Winsorized Means** dialog.

**Figure 38.5:** Trimmed / Winsorized Means Dialog

In the dialog, you choose the number of observations trimmed or Winsorized in each tail in (1/2)N and the percent of observations trimmed or Winsorized in each tail in (1/2)Percent. If you specify a percentage, the smallest integer greater than or equal to *np* is trimmed or Winsorized.

The **Density Estimation** button enables you to set the options associated with both parametric density and nonparametric kernel density estimation. Click on **Density Estimation** to display the **Density Estimation** dialog.

**Figure 38.6:** Density Estimation Dialog

If you select **Parametric Estimation:Normal**, a normal distribution with the sample mean and standard deviation is created. For the lognormal, exponential, and Weibull distributions, you specify the threshold parameter in the **Parameters:Theta:** entry field in the distribution output options dialog, as shown in Figure 38.4, and have the remaining parameters estimated by the maximum-likelihood estimates.

If you select a **Weight** variable, the weighted parametric normal density and weighted kernel density are generated. The parametric lognormal, exponential, and Weibull density are not computed.

The **Cumulative Distribution** button enables you to set the options associated with cumulative distribution estimation. Click on **Cumulative Distribution** to display the **Cumulative Distribution** dialog.

**Figure 38.7:** Cumulative Distribution Dialog

If you select **Fit Parametric:Normal**, a normal distribution with the sample mean and standard deviation is created. For the lognormal, exponential, and Weibull distributions, you specify the threshold parameter in the **Parameters:Theta:** entry field in the distribution output options dialog, as shown in Figure 38.4, and have the remaining parameters estimated by the maximum-likelihood estimates.

If you select a **Weight** variable, weighted empirical and normal cumulative distribution functions can be generated. The confidence bands, the parametric lognormal, exponential, and Weibull cumulative distributions, and tests for distribution are not computed.

Click on **OK** to close the dialogs and create your distribution analysis.

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