How to perform statistical analyses

After you have entered data in the spreadsheet, it is advised to save the data on disk. This is done by clicking Save as on the File menu. You will have to enter a name for your data file in the File selector box.

To load a data file from disk, click Open on the File menu. Next, select the name of the file in the File selector box. For example, you can select the data file Patients - sample data.mc1. This file contains data on length and weight for a number of persons.

When you want to obtain summary statistics for the variable Weight, click Summary statistics on the Statistics menu. The following dialog box appears on the screen.

Dialog box for Summary statistics

In this dialog box you can identify the variable to be analyzed.

You can click the button to obtain a list of variables.

Select variable

From this list you can select a variable by clicking the variable's name.

Select variable

If the variable requires a logarithmic or square root, or any other mathematical transformation, then you can enter a formula in the variable field:

SQRT(WEIGHT)

LOG(LENGTH)

or you can enter a formula combining different variables, e.g.

WEIGHT/LENGTH

By doing so, new variables will be added to the variables list: SQRT(WEIGHT), WEIGHT/LENGTH, etc..

Optionally, you may also enter a filter in the Filter field of the dialog box, in order to include only a selected subgroup of cases in the statistical analysis.

Select a filter

The filter may contain a combination of different criteria, using the AND and OR functions (see logical functions):

AND(LENGTH>160,LENGTH<170)

These expressions may make use of all mathematical and other spreadsheet functions available.

For an overview of mathematical operators and functions available in MedCalc, refer to the following pages: operators, mathematical functions, string functions, logical functions, and date functions.

After you have entered a filter in a dialog box (in order to include only a selected subgroup of cases in the statistical analysis), this filter will be "remembered" by the program and will be selectable in the Filter list.

After you have clicked OK, the following statistics are calculated and displayed in the results window:

Summary statistics

For more details about the displayed statistics, see Summary statistics in the Statistics menu.

Note that when you change the data in the spreadsheet, this will not automatically cause a recalculation of the displayed statistics, but you have to repeat the statistical analysis for the new data.

To facilitate this, use the Saved tests and graphs feature: by clicking in the toolbar you can save the analysis so you can recall the analysis later, possibly with new data. After you have clicked this button the graph is added to the Saved tests and graphs list in the Contents bar, with a default name, which you can edit.

Graphs

How to perform statistical analyses

Next

See also