Appendix 1.3

Appendix 1.3

Appendix 1.3
(See related pages)

Getting Started with MegaStat

MegaStat, which was developed by Professor J. B. Orris of Butler University, is an Excel add-in that performs statistical analyses within an Excel workbook. After it is installed, it appears on the Excel menu and works like any other Excel option. Instructions for installing MegaStat can be found on the CD-ROM that accompanies this text.

When you click on MegaStat on the Excel menu bar, the MegaStat menu appears as shown to the right. Most of the menu options display submenus. If a menu item is followed by an ellipsis (...), clicking it will display a dialog box for that option.

A dialog box allows you to specify the data to be used and other inputs and options. A typical dialog box is shown to the right.

After you have selected the needed data and options, click OK. The dialog box disappears, and MegaStat performs the analysis. Before we look at specific dialog boxes, we will describe some features that are common to all of the options. MegaStat use is intuitive and very much like other Excel operations; however, there are some features unique to MegaStat.

Data selection Most MegaStat dialog boxes have fields where you select input ranges that contain the data to be used. Such a field is shown in the dialog box just illustrated—it is the long horizontal window with the label “Input range” to its right. Input ranges can be selected using four methods:

Pointing and dragging with the mouse. Simply select the desired data by pointing to it, left-clicking on the first data item, and dragging the cursor to select the rest of the data as illustrated above.
Since the dialog box pops up on the screen, it may block some of your data. You can move a dialog box around on the screen by placing the mouse pointer over the title bar (colored area at the top) and then clicking and holding the left mouse button while dragging the dialog box to a new location. You can even drag it partially off the screen.
You will also notice that when you start selecting data by dragging the mouse pointer, the dialog box will collapse to a smaller size to help you see the underlying data. It will automatically return to full size when you release the mouse button. You can also collapse and uncollapse the dialog box manually by clicking the collapse (-) button at the right end of the field. Clicking the button again will uncollapse the dialog box. (Never use the button to try to collapse or uncollapse a dialog box.)
Using MegaStat’s AutoExpand feature. Pointing and dragging to select data can be tedious if you have a lot of data. When you drag the mouse down it is easy to overshoot the selection, and then you have to drag the mouse back until you get the area correctly selected. AutoExpand allows you to select data rapidly without having to drag through the entire column of data. Here is how it works:
1. Make sure the input box has the focus (that is, click in it to make the input box active). An input box has the focus when the insertion pointer is blinking in it.
2. Click in one cell of the column you want. If more than one column is being selected, drag the mouse across the columns.
3. Right-click over the input field or left-click the label “Input range” to the right of the input box. The data range will expand to include all of the rows in the region where you selected one row.
This procedure is illustrated on the next page. In the left screenshot, we have left-clicked on one cell in the column of data labeled WaitTime. In the right screenshot, we see the result after we right-click over the input field or left-click on the label “Input range.” Notice that the entire column of data has been selected in the right screenshot. This can be seen by examining the input field or by looking at the column of data.
With a little practice you find this is a very efficient way to select data. The only time you cannot use it is when you want to use a partial column of data. You should also be aware that the AutoExpand stops when it finds a blank cell; thus any summations or other calculations at the bottom of a column would be selected.
Note: When using these methods of data selection, you may select variables in an alternate sequence by holding the CTRL key while making multiple selections.
Typing the name of a named range. If you have previously identified a range of cells using Excel’s name box, you may use that name to specify a data range in a MegaStat dialog box. This method can be very useful if you are using the same data for several different statistical procedures.
Typing a range address. You may type any valid Excel range address—for example, A1:A101—into the input field. This is the most cumbersome way to specify data ranges, but it certainly works.

Data labels For most procedures, the first cell in each input range can be a label. If the first cell in a range is text, it is considered a label; if the first cell is a numeric value, it is considered data. If you want to use numbers as variable labels, you must enter the numbers as text by preceding them with a single quote mark—for instance, 2. Even though Excel stores times and dates as numbers, MegaStat will recognize them as labels if they are formatted as time/date values. If data labels are not part of the input range, the program automatically uses the cell immediately above the data range as a label if it contains a text value. If an option can consider the entire first row (or column) of an input range as labels, any numeric value in the row will cause the entire row to be treated as data. Finally, if the program detects sequential integers (1,2,3,...) in a location where you might want labels, it will display a warning message. Otherwise, the rule is that text cells are labels, and numeric cells are data.

Output When you click OK in a MegaStat dialog box, it performs some statistical analysis and needs a place to put its output. It looks for a worksheet named Output in the current Excel application. If it finds one, it goes to the end of it and appends its output; if it doesn’t find an Output worksheet, it creates one. MegaStat never changes the user’s worksheets; it only sends output to its Output sheet.

MegaStat attempts to format the output, but remember that the Output sheet is just a standard Excel worksheet and can be modified in any way. You can adjust column widths and change any formatting that you think needs improvement. You can insert, delete, and modify cells. You can copy all or part of the output to another worksheet or to another application such as a word processor.

When the program generates output, it adjusts column widths for the current output. If you have previous output from a different option already in the Output sheet, the column widths for the previous output may be altered. You can attempt to fix this by manually adjusting the column widths. Alternatively, you can make it a practice to always start a new Output sheet. The Utilities menu has options for deleting the Output sheet, for making a copy of it, and for starting a new one.

An example We now give an example of using MegaStat to carry out statistical analysis. When the instructions call for a sequence of selections from a series of menus, the sequence will be presented in the following form:

MegaStat: Probability: Counting Rules

This notation says that MegaStat is the first selection from the Excel menu bar; next Probability is selected from the MegaStat pull-down menu; and finally Counting Rules is selected from the Probability submenu.

Creating a runs plot similar to Figure 1.6 (data file: GasMiles.xls):

In the Descriptive Statistics dialog box, enter the mileage data in TABLE 1.8 into column A with the label MPG in cell A1 and with the 49 mileages in cells A2 through A50.
Select MegaStat: Descriptive Statistics.
Enter the range A1:A50 into the Input range box. The easiest way to do this is to use the MegaStat AutoExpand feature. Simply select one cell in column A (cell A4, for instance) by clicking on the cell. Then, either right-click in the Input range box or left-click on the label “Input range” to the right of the Input range box.
Check the Runs Plot check box.
Click OK in the Descriptive statistics dialog box.

MegaStat places the resulting analysis (in this case the runs plot) in an output worksheet. This is a standard Excel worksheet, which can be edited using any of the usual Excel features.

For instance, by right-clicking on various portions of the runs plot graphic, you can edit the plot in many ways. Here we have right-clicked on the chart area. By now selecting Format Chart Area, we are able to edit the graphic in a variety of ways.

In the Format Chart Area dialog box, we can add color to the runs plot, change fonts, and edit the plot in many other ways.

When we right-click on the chart area and obtain the previously shown pull-down menu, we can alternatively select Chart Options. The Chart Options dialog box allows us to edit chart titles, axes and axis labels, data labels, and many other chart features.

Our final edited runs plot as presented in the text is as follows.

We complete this appendix by demonstrating how MegaStat can be used to generate a set of random numbers (as in Example 1.1).

To create 100 random numbers between 1 and 2136 similar to those in Table 1.1(b):

Select MegaStat: Generate Random Numbers ...
In the Random Number Generation dialog box, enter 100 into the “Number of values to be generated” window.
Click the right arrow button to select 0 Decimal Places.
Select the Uniform tab, and enter 1 into the Minimum box and enter 2136 into the Maximum box.
Click OK in the Random Number Generation dialog box.

The 100 random numbers will be placed in the Output Sheet. These numbers are generated with replacement. Repeated numbers would be skipped if the random numbers are being used to sample without replacement.

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