Class Note for STAT 528 at OSU 08
Class Note for STAT 528 at OSU 08
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Date Created: 02/06/15
Stat 528 Winter 2008 Kaizar An introduction to MINITAB 1 Introduction MlNlTAB is a computing package for performing simple statistical analyzes The current version on the PC is 15 o MlNlTAB is no longer made for the Macintosh 0 MlNlTAB is also available for unix and linux systems but not on our system 0 These instructions should work with the version 10 and above there are some changes to the menus for displaying graphs in versions 14 and 15 To start MlNlTAB on a PC click on the start button select All Programs Minitab Solutions and then Minitab 15 Statistical Software 2 Getting help Select the menu HelpHHelp to bring up a help window There is help available on a variety of topics In particular there is help on handling les editing and manipulating data graphing using session and macro commands and most importantly doing statistics with MlNlTAB The Methods and Formulas7 subsection under References is especially helpful in explaining various statistical and computing terms 3 Using worksheets Data is stored in a worksheet Think of it as a spreadsheet o The variables are columns Variables can be given a name or are referred to by C1 C2 Remember to always name your variables 0 The individuals are stored in the numbered rows A case is an entire row of the variables A new worksheet called Worksheet 1 is available whenever you start the program If you need to create a new worksheet use the menu option File a New 0 A dialog box will appear select Minitab Worksheet and OK 0 The new worksheet will appear in the MlNlTAB program window 1 2 3 J 5 T 397 B 9 n 1 Figure 1 The MINITAB worksheet 31 A motivating example We consider data derived from a dataset presented in Mackowialc p A Wasserrnan s s and Levine M M 1992 A Critical Appraisal of 985 Degrees F the Upper Lirnit of the Norrnal Body Temperature and Other Legacies of Carl Reinhold August Wunderlich Jamaal of the Amenca39 Medzcol Assoczomm 268 157871580 The data are a randorn sample of 130 individuals For each individual the body ternperature in degrees Fahrenheit and heart rate in beats per rninutes bprn were rneasured The gender for each subject was also recorded If you wanted to enter the data you would 0 Select a colurnn for the rst variable eg c1 o Type the name of the variable below the column number eg Body temperature Fahrenheit the colurnn width of the worksheet increases to t longer narnes 0 You could then enter the body temperatures in rows 1 to 130 Instead we will load the data in from a le 32 Loading and saving data Use the File gt Open Worksheet option to load saved data into MINITAB Datasets for this class are available from httpwwwstatosueduNekaizarcourseSSZB The data for this exalnple is linked under Normal Temperatures You can import data from different sources eg ASCII text le by changing the Files of Type option in the Open Worksheet dialog To save the current worksheet use the menu option File a Save Current Worksheet 0 The rst time you need to enter a lename for the worksheet It helps to store your data and work in a new folder for each homework pro ject you are working on To save the current worksheet under a different lename use the option File a Save Current Worksheet As 4 Graphical summaries of data 41 Histograms To produce a histogram of Body temperature Select Graph a Histogram Choose the Simple version of the histogram you can try more complicated histograms later A dialog box now appears This is how you set up your plot ln graph variables under X you select the variables you want to produce a histogram of Either 0 type the variable number eg C1 into the box or o in the right hand panel click on C1 Body temperature Fahrenheit and choose Select Click on Scale to change the appearance of the scales In particular under the YScale type you can select between Frequency Percent and Density Press OK to produce the plot 7 a new graph window will appear with the resulting graph You can only change the X scale after you have created the plot Double click on the X scale to change the scale Right clicking the X scale of the histogram and selecting Edit XScale will also work Changing the binning can be especially useful You can edit any other feature of a graph in a similar way by doubling clicking on it To include your graph in a word processed document 0 Select the graph you are interested in o Press the right mouse button a menu appears Select Copy graph 0 Paste the plot into your favorite word processor using Edit a Paste 42 Boxplots Use Graph a Boxplot to create boxplots This is similar to the histogram command Choose the One Y Simple plot for histograms of one variable To produce a sideby side boxplot of the body temperature by gender use the One Y With Groups command Enter C1 Body temperature for the Graph variables and C3 Gender for the Categorical variables for grouping Then press OK 43 Bar and Pie charts Now we consider a different dataset Suppose we have the following summary data stored in a Minitab worksheet C1 T C2 gender 6 ount female 4 male 3 To make a bar chart of these data use the Graph a Bar Chart command Choose Value from a table for the Bars represent option and click OK Enter count for the Graph variables and gender for the Categorical variable and click OK If your data is represented instead as C1 T gender male female female male male female female choose Counts of unique values for the Bars represent option click OK and then enter gender in the Categorical Variables box If you want to change the Y scale then double click on the Y axis and after selecting Position of ticks enter the Y label values If you do not want a gap between the X values ie a histogram not a bar chart double click on the Y axis and de select Gaps between clusters and enter a value of O Pie charts are similar Use the Graph a Pie Chart menu command 44 Time series plots Will use the Lake Huron levels dataset from the website The dataset contains the annual measure ments of the level in feet of Lake Huron 1875 1972 Source Brockwell P J and Davis R A 1996 Introduction to Time Series and Forecasting Springer New York Select Graph 7 Time Series Plot and then the Simple plot Choose level for the series Now select TimeScale choose Stamp and enter year for the Stamp Columns Click OK to close the TimeScale dialog box and then OK again to produce the graph 5 Numerical summaries To summarize our body temperatures dataset Select Stat a Basic Statistics 7 Display Descriptive Statistics A dialog box now appears ln variable select the variable you want to summarize Either 7 type the variable number eg C1 into the box 7 or in the right hand panel click on C1 body temperatures and choose Select To produce the summaries click OK in the dialog You can also produce plots of the data by clicking on Graphs Do not use this option These graphs contain extra elements that are hard to interpret 7 Use the commands you learned earlier The summaries are presented in the Session window Results for NURMALTEMPERATURES MTW Descriptive Statistics Body temperature Fahrenheit Variable N N Mean SE Mean StDev Minimum Q1 Median Q3 Body temperature Fahren 130 0 98249 00643 0733 96300 97800 98300 98700 Variable Maximum Body temperature Fahren 100800 Here are the headings we will de ne all these quantities in the course 0 N number of observations o N number of missing values 0 Mean sample mean 0 StDev standard deviation 0 SE Mean standard error for the mean 0 Minimum sample maximum 0 Q1 rst sample quartile 0 Median sample median 0 Q3 third sample quartile 0 Maximum sample maximum To produce a summary of the body temperatures by gender enter C3 Gender in the By variables of the Display Descriptive Statistics dialog box Descriptive Statistics Body temperature Fahrenheit Variable Gender N N Mean SE Mean StDev Minimum Q1 Median Body temperature Fahren female 65 0 98394 00922 0743 96400 98000 98400 male 65 0 98105 00867 0699 96 300 97 600 98100 Variable Gender Q3 Maximum Body temperature Fahren female 98 800 100800 male 98 600 99 500
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