StatWizard Summary The StatWizard is designed to serve several functions: 1. It assists new users in entering data to be analyzed. 2. It provides a search facility to help locate desired statistical procedures. 3. It contains a mechanism to apply one or more analyses to each level of a specified BY variable. The StatWizard appears whenever STATGRAPHICS is loaded, unless the user selects to suppress it. In addition, the StatWizard may be invoked at any time by pressing the button with the wizard s cap on the main toolbar. StatWizard Screen for Empty Datasheet If the active datasheet is empty when the StatWizard appears, a dialog box is displayed to assist in entering data. Select one of three options: 2009 by StatPoint Technologies, Inc. StatWizard - 1
STATGRAPHICS Rev. 4/1/2009 Enter New Data or Import It from an External Source: Select this option if you wish to enter data into the datasheet by hand or retrieve it from a file or database. Design a New Experiment, Gage Study, Control Chart, or Sampling Plan: Select this option to construct a statistically-designed study before collecting any data. Perform an Analysis that Does Not Require Data: Select this option for a list of analyses that do not require inputting any data. Adding Data to a Datasheet If Enter New Data or Import It from an External Source is selected on the initial box, a second dialog box is displayed to help users put that data into a STATGRAPHICS datasheet so that it can be analyzed: Specify the location of the data: I Want to Type It In: indicates that you wish to enter new data by hand. STATGRAPHICS will then prompt you to specify the columns to be created in the datasheet by displaying the dialog box used to specify column attributes: 2009 by StatPoint Technologies, Inc. StatWizard - 2
Specify a name, comment, and type for each column. Names may have from 1 to 32 characters and may contain any character not used in an algebraic expression. Spaces are fine, but plus signs (+), parentheses, and other characters that might appear in an algebraic statement are not allowed. Once all the columns have been defined, press Cancel, at which time the datasheet will come to the forefront so that you can begin typing in your data. In an Existing Data File, Database, or on the Windows Clipboard: indicates that the data has already been entered elsewhere. The StatWizard then displays the STATGRAPHICS DataBook Properties page: 2009 by StatPoint Technologies, Inc. StatWizard - 3
Select the datasheet into which the data is to be read and then press Open. Indicate the location of the data: Then follow the prompts to read the data. For more information on reading data, see the Data Files and StatLink documentation. In a Data Source Linked to an Existing StatFolio: indicates that a StatFolio exists that is linked to the desired data. The StatWizard will prompt you for the name of the StatFolio. After the data is read or the columns created, the StatWizard will close so that you can examine the datasheet. 2009 by StatPoint Technologies, Inc. StatWizard - 4
Already Loaded in a STATGRAPHICS Datasheet: indicates that the data is already loaded into one of the datasheets. When OK is pressed, the StatWizard will move to the dialog box listing the statistical analyses. Designing a Statistical Study When first starting the program or whenever the DataBook contains no data, the start-up StatWizard dialog box offers a selection labeled Design a New Experiment, Gage Study, Control Chart, or Sampling Plan. This option lets you set up a statistical study before data is collected. The type of study is selected using a second dialog box: The options will invoke procedures that: 1. Determine an Adequate Sample Size to Characterize a Population: selects the sample size n needed to estimate or test a hypothesis about a normal mean, standard deviation, binomial proportion, or Poisson rate. 2. Determine an Adequate Sample Size to Compare Two or More Populations: selects the sample size needed to compare or test a hypothesis about two normal means, two standard deviations, two binomial proportions, or two Poisson rates. It will also select the sample size for a oneway analysis of variance. 2009 by StatPoint Technologies, Inc. StatWizard - 5
3. Design an Experiment: starts the Design Creation procedure in the DOE section of STATGRAPHICS. Various types of designs can be created, including screening designs, response surface designs, mixture experiments, D-optimal designs, designs with both inner and outer arrays, and designs involving categorical factors. 4. Select a Screening Design Experiment: assists in determining adequate sample sizes when a screening design is desired. 5. Set up a Gage R&R Study: creates a datasheet of the form required to perform a gage analysis of variable or attribute data. 6. Design a Control Chart: assists in choosing subgroup sizes or smoothing parameters for various types of control charts. 7. Develop an Acceptance Sampling Plan for Variable Data: creates an acceptance sampling plan for measurement data. 8. Develop an Acceptance Sampling Plan for Attribute Data: creates an acceptance sampling plan for PASS/FAIL data. When the OK button is pressed, the StatWizard will locate the necessary procedure on the main menu and display its data input dialog box. Performing an Analysis that Does Not Require Data When first starting the program or whenever the DataBook contains no data, the start-up StatWizard dialog box also offers a selection labeled Perform an Analysis that Does Not Require Data. When you select this option, a dialog box will be displayed listing those procedures that do not require data to be entered into the datasheet before they are run: 2009 by StatPoint Technologies, Inc. StatWizard - 6
The options invoke procedures that: 1. Test a Hypothesis about a Single Population: tests hypotheses about a normal mean, a normal standard deviation, a binomial proportion, or a Poisson rate. 2. Test a Hypothesis about Two Populations: tests hypotheses about two normal means, two normal standard deviations, two binomial proportions, or two Poisson rates. 3. Determine Tolerance Limits for a Normal Distribution: find limits which bound a specified percentage of a normal distribution given a sample size, a sample mean, and a sample standard deviation. 4. Examine a Probability Distribution: plots any of 45 probability distributions, calculates probabilities or critical values, and generates random numbers. 5. Plot a Response Surface: creates a surface or contour plot from a user-specified equation. 6. Create an Empty Chart for Plotting Data by Hand: draws a chart with axes, labels, and vertical and/or horizontal lines but no data. 7. Draw a Process Map: creates a process map or flow chart. 2009 by StatPoint Technologies, Inc. StatWizard - 7
8. Convert between Six Sigma Metrics: converts between Z-scores, DPM, Cpk, and the Sigma Quality Level. 9. Set System Preferences: sets default values for many system options. Selecting An Analysis Once data has been loaded into the datasheet, the StatWizard may be accessed by pressing the button with the wizard s cap on the main toolbar. The first dialog box that appear is designed to help select the desired statistical analysis. The following options are available: Select Analysis Based on Type of Data: A sequence of dialog boxes will be displayed, first requesting the name of the columns containing the data to be analyzed and then displaying a list of analyses that are relevant for the specified type of data. This option is useful is you do not know the specific type of analysis that you wish to apply. Select Analysis by Name: The analyses are listed in alphabetical order. Select the desired analysis and press OK. 2009 by StatPoint Technologies, Inc. StatWizard - 8
STATGRAPHICS Rev. 4/1/2009 Select a SnapStat: Select one of the SnapStats and press OK. SnapStats are special analyses that produce a single page of preformatted tables and graphs. They do not have as many options as standard analysis procedures, but they are very easy to use. Search: displays a list of many statistics and tests calculated by the program. When you pull down the list and select a statistic, the analyses listed under Select Analysis by Name are changed to include only those procedures that calculate the selected statistic. Select from the Following Quick Picks: lists many of the most frequently used analyses. Select an analysis and press OK. If you select any option except Select Analysis Based on Type of Data, you will be taken to that analysis when you press the OK button. Otherwise, additional dialog boxes will be displayed, the first of which requests the names and type of data that you wish to analyze: Specify: Data or Response Variables (Y): one or more response variables containing the values to be analyzed. If only one column is specified, it must be entered here. Type: the type of data contained in the response variables. The analyses displayed in subsequent dialog boxes depend on this choice. 2009 by StatPoint Technologies, Inc. StatWizard - 9
STATGRAPHICS Rev. 4/1/2009 Quantitative Explanatory Factors (X): any quantitative factors that are to be used to predict the response variables. In a regression, the independent variables go here. Categorical Explanatory Factors (X): any non-quantitative factors that are to be used to predict the response variables. In an ANOVA, the explanatory factors go here. Case Labels: a column containing labels for each of the observations (rows). The next dialog box allows you to subset a subset of the rows in the datasheet, if desired: Most of the options are self-explanatory. Two interesting options are: 1. Rows for which: restricts the analysis to rows for which the specified condition holds. 2. Each Unique value of: a separate analysis will be created for each unique value in the column specified. Some analysts refer to such a variable as a BY variable. You will then be asked if you wish to transform any of the variables. If so, a dialog box will be displayed from which to select the desired transformation, first for the response variables and then for the quantitative explanatory factors: 2009 by StatPoint Technologies, Inc. StatWizard - 10
Note that the Arc Sin Square Root transformation is sometimes used when the data are proportions between 0 and 1 in order to stabilize the variance. Finally, a dialog box will be displayed listing all procedures relevant for the type of data input. A typical dialog box is shown below: 2009 by StatPoint Technologies, Inc. StatWizard - 11
Select one or more analyses and press OK. The program will indicate how many windows will be created and ask your consent. If you give it, the analyses the windows will be created and the analysis will be run. 2009 by StatPoint Technologies, Inc. StatWizard - 12