Stat Computing > Statistica > Notes

Statistica Class Notes
Exploring Data

1.0 Demonstration and explanation

We will begin by getting the descriptive statistics for some of the variables.

• Statistics
   Basic Statistics/Tables
    Descriptive Statistics
     OK
      Variables
       select gender read write math science
        OK
         Summary

Now we will do the same thing, but we will only look at that the records for students who earned reading scores of 60 or above.

• Data
   Subset/Random Sampling...
    Variables
     click on "Select all"
      OK
       click on "Use selection condition expression"
        Cases
         check "enable selection conditions"
          click on "Specific, selected by" box in the "include cases" box
          type read >= 60 into the Expression box
           OK
            OK

• Statistics
   Basic Statistics/Tables
    Descriptive Statistics
     OK
      Variables
       select gender read write math science
        OK
         Summary

For the next example, we will select a different set of cases to be analyzed.  This time we only want to analyze the data from the students in the academic program.

• Activate the full data set by clicking on it once.

• Data
   Subset/Random Sampling...
    Variables
     click on "Select all"
      OK
       click on "Use selection condition expression"
        Cases
         click on "Specific, selected by" in the "include cases" box
         type prgtype = "academic" into the Expression box
          OK
           OK

• Statistics
   Basic Statistics/Tables
    Descriptive Statistics
     OK
      Variables
       select gender read write math science
        OK
         Summary

Instead of selecting cases based on the value of a variable, we will now look at cases that fall into a range.  We will specify the range of cases that we want included in the analysis.

• Activate the full data set by clicking on it once.
  

• Data
   Subset/Random Sampling...
    Variables
     click on "Select all"
      OK
       click on "Use selection condition expression"
        Cases
         click on "Specific, selected by" in the "include cases" box
          type 1-40 into the "or case number" box
           OK
            OK

• Statistics
   Basic Statistics/Tables
    Descriptive Statistics
     OK
      Variables
       select gender read write math science
        OK
         Summary

Now we are going to move on to some different types of analyses.  We will compare the means of the variables read, write, math and science broken down by prgtype. 

• Activate the full data set by clicking on it once.

• Statistics
   Basic Statistics/Tables
    Breakdown and one-way ANOVA
     OK
      Variables
      select read write math science as the dependent variables
      select prgtype as the grouping variable
       OK
        click on "codes for grouping variables"
         click on "All"
          OK
           OK
            under "Quick" tab, click on "Detailed two-way tables"

We can see the box plots for these variables broken down by our grouping variable.

• click on "Categorized box and whisker plot"
   click on "Select All" to select all of the variables
    OK

We can do some basic graphics, such as stem and leaf plots, boxplots and histograms.

• Statistics
   Basic Statistics/Tables
    OK
     Variables
      select write
       OK
        under the "Normality" tab, click on "Stem and leaf" in the lower
        right-hand corner

• Statistics
   Basic Statistics/Tables
    OK
     Variables
      select write
       OK
        under the "Categ. plots" tab, click on "Categorized box 
        and whisker plots"
         select gender as the "first variable"
          OK
           click on "All"
            OK

• click on the "Descriptive Statistics" window (which may be minimized
  in the bottom left of the window)
   under the "Normality" tab, click on "Histograms"
  

• click on the analysis window (which may be minimized in the bottom 
  left of the window)
   Variables
    select ses
     OK
      click on "Histograms"
   

• click on the analysis window (which may be minimized in the bottom 
  left of the window)
   Variables
    select write
     OK
      click on "Histograms"

Now we will look at some crosstabulations and correlations.

• click on the analysis window (which may be minimized in the bottom 
  left of the window)
   click on "Cancel"
    click on "Tables and banners"
     OK
      under the "Crosstabulation" tab, click on "Specify tables 
      (select variables)"
        select prgtype for list1 and ses for list2
         OK
          OK
           Summary

• click on the analysis window (which may be minimized in the bottom 
  left of the window)
   click on "Cancel"
    click on "Cancel"
     click on "Correlation matrices"
      OK
       click on "One variable list"
        select read write math science
         OK
          Summary  

• click on the analysis window (which may be minimized in the bottom 
  left of the window)
   click on the "Pairwise" radio button in the "MD deletion" box
   in the lower left-hand corner
    Summary

Let's do some more graphics.  The graphical representation of a correlation is a scatterplot, so let's try a couple of those.

• Graphs
   Scatterplots
    under the "Quick" tab, click on "variables"
     select write for the y-axis and read for the x-axis
      OK
       in the "Fit type" box, uncheck "Linear"
        OK

• click on the analysis window (which may be minimized in the bottom 
  left of the window)
   under the "Appearance" tab, click on "Frequency" under "Graph type"
    OK

• Graphs
   Matrix plots
    Variables
     select read math science write
      OK
       OK

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