# 1.5.4 - Minitab: Descriptive Statistics

## Descriptive Statistics Section

Let's perform some basic operations in Minitab. Some of the examples below are repeats of what we did by hand in earlier lessons while others are new.  First, we saw previously how you can enter data into the Minitab worksheet by hand, we will now walk through how to load a dataset into Minitab from an Excel file.

For the examples in this section, download the minitabintrodata.xlsx spreadsheet file. Save the file locally (if using Minitab installed on the computer you are using) or save the file in your PASS space if using WebApps.

Open Minitab, then using the Minitab menus at the top of the application, select the option:

• File > Open Worksheet .
• In the ‘Files of Type’ field click the drop down arrow and select Excel .
• In the ‘Look In’ field use the drop down arrow to locate the saved Excel data file.
• Double click the file and the data should open in the Minitab worksheet (the window that looks similar to an Excel spreadsheet).

With the data in the Minitab worksheet, you can then perform any number of procedures. First, we obtain some basic descriptive statistics.

### Descriptive Statistics

With the data from the Excel spreadsheet file into your Minitab worksheet window, you should notice that all columns are labeled ‘Cx’ where the ‘x’ is a number. Some of these are followed by a ‘-T’. Those columns with the ‘-T’ indicate that the data in this column are considered text or categorical data. Otherwise, Minitab recognizes the data as quantitative. If the operation you conduct in Minitab only functions on a certain variable type (e.g. calculating the mean can only be done on quantitative data) then only columns of that data type will be available to use for those operations.

## Example 1-10 Hours Data Section

Let's use Minitab to calculate the five number summary, mean and standard deviation for the Hours data, (contained in minitabintrodata.xlsx). And, as you will see, Minitab by default will provide some added information.

1. At top of the Minitab window select the menu option Stat > Basic Statistics > Display Descriptive Statistics

2. Once this dialog box opens your cursor should be blinking in the 'Variables' window. If not, simply click inside this part of the dialog box. The only variables you should see in the left side window are columns of quantitative data (the two price columns, age, and hours). To enter a variable from the left hand window into the Variables window you can either double-click that variable or click the variable to highlight it and then click the 'Select' button. Do so with the variable 'Hours'.

3. With the variable 'Hours' in the 'Variable' window click the 'OK' button.

The following output should appear in the Session window above the worksheet.

#### Statistics

Variable N N* Mean SE Mean StDev Minimum Q1 Median Q3 Maximum

Hours

50 835 16.00 1.19 8.45 4.00 9.00 15.00 22.25 34.00

The mean, standard deviation (StDev), etc. should be the same values as those calculated in the practice problems. Minitab also gives the size of the sample used to create these statistics (N), and the number of observations from this data that were missing (N*).

These statistics are the default statistics. Additional basic descriptive statistics are also available such as trim mean and coefficient of variation (CV).

## Example 1-11: The Coefficient of Variation (CV) Section

To get the CV values for the Price per Sheet and Price per Roll an example found in an earlier lesson, (data contained in minitabintrodata.xlsx).

1. Open Minitab and return to Stat > Basic Statistics > Display Descriptive Statistics.
2. Enter both variables into the Variables window. That is, both 'Price_Roll' and 'Price_Sheet' should be in the Variables window.
3. Click the Statistics tab and then check the box for 'Coefficient of Variation' (notice the other statistics available!) and click OK.
4. Click OK again.

The output will include the same statistics as the example above plus the CV values, (it will be titled 'CoefVar').

### Descriptive Statistics: Price_Roll, Price_Sheet

#### Statistics

Variable N N* Mean SE Mean StDev CoefVar Minimum Q1 Median Q3 Maximum

Price_Roll

24 861 0.9196 0.0864 0.4233 46.03 0.5300 0.6075 0.7750 0.9500 1.9800
Price_Sheet 24 861 0.01134 0.00113 0.00553 48.78 0.00610 0.00753 0.00995 0.01490 0.03180