Fitting Continuous Distributions - Parameters Tab

Select the Parameters tab of the Fitting Continuous Distributions dialog box to access the options described here. The boxes on this tab are available only after a variable has been selected. On the Parameters tab, select the number of categories, upper and lower limits, and the values of the parameter(s) of the selected distribution. After entering these figures, click the Summary: Observed and expected distribution button on the Quick tab to display your results. You can also display the results in histogram format by clicking the Plot of observed and expected distribution button on the Quick tab.

Number of categories

Use the Number of categories box to control the way in which the frequency distribution is computed (and the histogram of observed data is drawn). Specify the number of categories in the frequency table or histogram. Note that the maximum number of categories allowed is 50.

Lower limit

Use the Lower limit box to specify the lower limit. Except for the Normal and Rectangular distributions, STATISTICA will only allow lower limits equal to or larger than zero (with the former being ignored when the distribution is Log-Normal). The lower limit must be smaller than the upper limit. Note that STATISTICA will produce an appropriate error message when an invalid value of the lower limit is entered.

Upper limit

Use the Upper limit box to specify the upper limit. Except for the Normal and Rectangular distributions, STATISTICA will only allow upper limits equal to or larger than zero (with the former being ignored when the distribution is Log-Normal). Note that STATISTICA will produce an appropriate error message when an invalid value of the lower limit is entered.

Note:  Data cases falling to the left of the lower limit are treated as  accumulated counts in the first bin. Similarly, data cases falling to the right  of the lower limit are regarded as accumulated counts in the last bin. For  example, if the data set contains case values (1, 2 , 3) with the lower limit set  to 1, the count in the first bin will be 3 and not 1.

Parameter One

When a distribution is chosen, the Parameter tab will display one of the following parameters depending on the type of distribution chosen. Enter the Mean value for the Normal and Lognormal distributions, Minimum range for the Rectangular distribution, Lambda for the Exponential distributions, Scale for the Gamma distribution, and Degrees of Freedom for the Chi-Squared distributions. Note that STATISTICA will produce an error message if an invalid value of this parameter is entered.

Parameter Two

When a distribution is chosen, the Parameter tab will also display one of the following parameters depending on the type of distribution chosen (if applicable). Enter the Variance value for the Normal and Lognormal distributions, Maximum range for the Rectangular distribution, and the Shape parameter for the Gamma distribution.

Observed mean. Displays the observed mean of the selected variable.

Observed variance. Displays the observed variance of the selected variance.

Set to default

Click this button to restore the defaults.