A BRIEF INTRODUCTION TO MINITAB STATISTICAL SOFTWARE
Carl Lee
Note: This PC lab does not allow anyone to save files to the hard disk other than your Z-drive.
You should bring your own 3.5" disket to class.
To start Minitab
Go to Start Menu
, Choose Programs , Go to Minitab 12, and click on Minitab to open the program.
Minitab consists of four windows: session, data, info and history windows.
By default, the session and data windows are open when you start Minitab.
Data Window: is for creating your data set.
Session Window: is for the statistical results.
Info Window: is for the information of data variables you created in the data window. History Window: is for saving the Minitab commands that you generated during the analysis.
Graph window is not a default window. However, if you create a graph, it will appear as a stand-alone window, of which you can make any editing.
You can locate any window from the "Window" menu on the top of your screen.
At a given time, only one window is active. By clicking on a window, it will be the active window.
A. Input, Output, and Data Manipulation
Because your data can come in many forms, Minitab provides many ways for you to enter data into the worksheet.
- Creating data file using minitab worksheet
(1) Click on the data Window to make it the active window. The worksheet is similar to a spreadsheet. C1, C2, C3... stand for Col 1, Col 2, Col 3. Columns are for variables, and rows are for cases (starting 1,2,3...)
(2) Defining Variable Names
The row above the Row 1, underneath the C1, C2, C3, is for defining variable names. The sign
" The sign "" indicates you are entering data from up and down within the same column.
(3) Enter the data values by moving the cursor to the starting cell where you want to enter your data, and begin to enter data values.
(4) Edit the data values: If an incorrect data value is found, Move the cursor to the cell and enter the correct data value.
(5) Save the worksheet: Go to File menu, go to ‘
save worksheet (as)’.Example:
To create the data set with:
Variables: SS Name Test 1 Test 2
Values: 3344 AABB 80 92
4111 ABCD 78 *
1532 XYZ 95 98
8833 WABC 72 64
You may use SS, Name, Test 1, Test 2 as variable names and enter them underneath C1,C2, C3, C4. Then, enter data points into row 1,2,3, and 4 accordingly.
There are two types of Data Values:
(1) Numeric: Such as SS, Test 1, Test 2, in the above example. A missing numeric value is defined as ‘*’ in Minitab
(2) Text: such as the variable NAME in the above example.
Minitab will add "-T" to the column # automatically if the variable in column 2 is an "Text" variable. You will find C2 becomes C2-T
- You can copy and paste data values within and from other worksheets:
You can copy a fraction of a data set and paste it to different columns of the same worksheet or paste it to a different worksheet by:
Highlight the area,
- You can open a worksheet that was created before from a file :
Go to File menu, then, choose Open Worksheet
For example:
Generate a set of patterned data: choose Calc, Set Patterned Data
Generate a set of data from normal distribution: choose Calc, Random Data, Normal
How to open worksheet
- If you have created a data file and saved it in a disket or a hard drive.
Go to File , click on Open Worksheet
Be sure the correct file type appears in the List Files of Type box.
Highlight the file you want to open click Open to open the file
How to read a Text Files
You can open text files in two ways:
Go to File, Open Worksheet, choose the correct file type in the "List files of type" box.
What is a Worksheet in Minitab?
The worksheet consists of three parts:
columns [ up to 1000 columns: C1, C2, . . ., C945, ...]: This is the Data Window.
stored constants [up to 1000 stored constants: K1, K2, . . .]
matrices [up to 100 matrices: M1, M2, . . .]
Minitab automatically assigns the values of missing, e, and p to the last three stored constants:
k998 = *; k999 = e = 2.71828; k1000 = p = 3.14159. These values can be changed if you wish.
Save Worksheet (As)
To save all the worksheet data in a file, choose File, click on Save Worksheet (As)
To save your analysis, including graphs and output in the session window,
choose File, click on Save Window As [This can only hold up to 15000 lines at one time.
Save worksheet allows different formats to save your data. Some of these formats are
- Minitab saved worksheet
- Minitab Portable worksheet
- Microsoft Excel
- Text (ASCII) file
Print Window (or Save Window)
To print the contents of the session, data, info, graph, or history window - whichever is active,
choose File, click on Print Window. (Save Window)
Print selection (or save selection as )
If you want to print (save) only part of the results in the session Windows: Highlight the part , go to File menu, click on Print selection, (or save selection as)
Display Data.
To display data on your session window:
Go to Manip, click on Display Data.
Data Manipulation.
For Mathematical expressions, choose Calc, click on Calculator.
To delete rows, choose Manip, click on Delete Rows
To erase variables, choose Manip, click on Erase Variables
To convert column from Text status to numeric status, choose Manip, click on
To code data values, choose Manip, click on Code to redefine a new variable using an existing variable.
To sort one or more columns of data, choose Manip, click on Sort.
Another common situation for using CODE is when we are trying to collate the categories of a variable or to redefine a continuous variable in to a categorical variable:
For example, AGE, say stored in C1, ranges from 30 to 69. We would like to group ages into 4 groups and store the categories in C2:
Group 1: 30-39
Group 2: 40-49
Group 3: 50-59
Group 4: 60-69
This can be easily done by CODE.
Go to Manip, click on CODE, enter 30:39 for old values and 1 for new.
40:49 for old values and 2 for new, etc., enter the result stored in C2.
The final result is in C2, consisting of values 1,2,3,4.
To set patterned data.
Go to calc, click on Make patterned data, fill the boxes. "Make patterned data" is a very useful command. We can use it to create a sequence of data values such as 10 1’s, 20 2’s, etc. It is useful for creating subscription or indicator variables.
Note: in the Make patterned data dialog, "Repeat the whole list" is to repeat the entire list as created in the " repeated each value". For example, for the same example, if we enter 3 in the "repeat the whole list", the final result in C3 is 20 1’s, 20 2’s, 20 1’s, 20 2’s, 20 1’s , 20 2’s. That is the whole list of 20 1’s and 20 2’s are repeated 3 times.
To use Row Statistics
:Go to calc, click on row statistics, choose the statistics you want to compute, select variables for input variables, enter a new column to store the result.
How to edit the data analysis results
in the session windowBy default, the output in the Session Window is editable. All you need to do is click on the Session, and begin to edit your output.
How to edit a graph.
Suppose you create a histogram. Usually, it is not a publishable form. You need to edit the graph by adding title, changing axes, changing graphs etc.
To create a Histogram for scores in C1:
Go to graph, Histogram, select C1 and click "selection" button for first graph
( You can create more than one histogram).
The "DATA Display" allows you to define how you would like to display the data.
Annotation, frame, region give you selections for setting up your graph. All of the data display attributes, annotation, and any commands that control the appearance can be edited later using graph editor. So, it is usually easier to edit your graph later when you actually see the graph.
‘Options’ provides you various way of constructing your histogram. As you click on "options" you see you can choose the type of histogram, intervals, and vertical histogram or horizontal histogram.
Note: Most of the graphs have similar dialog, which give you opportunity to select/ edit data display, annotations, frame, regions, and some options.
How to edit a graph, such as Histogram.
Once you created the histogram, click on the graph to make it the active window.
Then, Click on the graph twice, you will see tool palette and attribute palette appeared on the graph ( They can also be show/hide from the Editor menu) Go to Editor, click on show/hide tool palette, or attribute palette.
Some common actions used to edit a graph:
(a) The tool and attribute palette allows you to:
(1) Activate any part of the graph: By clicking on the part, it is activated with a dotted box around. Click on any other spot, the dotted box disappears and the part is no longer activated.
To change the box size of the activated part, you move the cursor to the dots on the edge, press the mouse, drag it around to change the size of the box.
To move the position of activated part: Move cursor inside the dotted box, press the mouse, drag it around to move the part around.
To edit a text: Click on the text twice, you see a text editor dialog. you can change the words or numbers as you wish.
(3) Add a title or any new text to the graph:
Click "T" button in the tool pallet, enter your text
(4) Change the font, color, font, size, thickness of a line, fills of a block, types of dots or lines, etc: Using the attribute palette: first activate the part of the graph to be edited, click on the appropriate button in the Attribute palette, then select your choice
(5) Activate a large area of the graph or the entire graph at once:
Move the cursor to the one end of the graph, press the mouse, then drag to the other end to activate the intended large part of the graph or the entire graph.
NOTE: This is very useful. For example, we would often like to change the font of the entire graph.
(6) Rotate the Marks on X-axis: The marks on the X-axis often are overlapped with the graph, which are not readable. To rotate the marks, first , activate the entire marks using the approach in (5), then, go to Editor, choose Rotate left (or right), choose the degree of rotation.
(7) Unlock data points in the graph: By default, the data points in the graph should be locked Sometimes, you may need to move/edit these data points in the graph. Go to Editor, choose Unlock Data Display, the data points are now editable.
It is important to remember to lock the display after the editing to prevent accidental wrong doing.
(8) Save Graph: Go to File menu, choose Save Graph as.
How to integrate Minitab statistical output, graphs into a report, say, using Microsoft Word.
The Minitab statistical output is a text file. There is easy to copy the output text file from the Minitab session window and paste it on to any Microsoft document. You first highlight the output in the Session Window, then, go to Edit, choose Copy. Then open Microsoft Word, paste the output to your Word file.
To copy and Insert a graph from Minitab to Word:
Click on the Graph you wish to copy, then go to Editor menu, click on ‘View’.
Go to Edit Menu, click on ‘Copy Graph’ to copy the graph.
Go to your Words file, and paste the graph to the appropriate position in your report.
NOTE: Minitab allows two modes of a graph. One is the ‘Edit’ mode; the other is the ‘View’ mode. To copy a graph, you MUST make the Graph at the ‘View’ mode under the ‘Editor Menu’.
B. Basic Descriptive and Graphical Statistical Analysis
Basic tools are:
Descriptive Statistics.
Graphs
Character graphs: A text version of graph displayed in session window along with output.
To construct a histogram, choose Graph, click on Histogram [This is high resolution graph.] For low resolution graph, you need to select Histogram from Character Graphs.
To construct a pie chart, choose Graph, click on Pie Chart.
To construct a stem-and-leaf plot, go to Graph, choose Character graphs, choose Stem-Leaf display..
To construct a box-plot, choose Graph, click on Boxplot.
Numerical Descriptive Statistics.
To produce descriptive statistics, go to Stat, go to Basic Statistics, click on Display Descriptive Statistics.
One can produce descriptive statistics for each level of a BY variable. The results are in session window.
NOTE: Under Display Descriptive Statistics, if one selects "Graphical form" under "Display options" the command gives results in graph windows. Each Graph includes a histogram with an overlaid normal curve, a box plot and confidence intervals for the mean and median, and a table of statistics.