# Fitting Discrete Distributions - Parameters Tab

Select the Parameters tab of the 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, you can 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 the 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. This box is available in any chosen distribution.

Lower limit. Use the Lower limit box to specify the lower limit. This box is available in any chosen distribution and STATISTICA will produce an error message when an invalid value of the lower limit is entered.

Upper limit. Use the Upper limit box to specify the upper limit. This box is available in any chosen distribution and STATISTICA will produce an error message when an invalid value of the upper limit is entered.

Parameter. When a distribution is chosen, the Parameter tab will display one of the following parameters depending on the type of the discrete distribution chosen. Note that you can modify the original (observed) values of these parameters. However, STATISTICA will produce an error message if an inappropriate value is chosen.

Number of trials (positive integer). Use the Number of trials box to specify the number of trials for the

Lambda (>0). Use the Lambda box to specify the Lambda value for the Poisson distribution.

Parameter p (<=0 and >=1). Use the Parameter p box to specify the parameter p value for the Geometric or Bernoulli distributions.

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.