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How to Apply Independent Samples Column Means and Proportions Tests to a Table

Oliver Harrison
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Introduction

This article describes how to go from a standard crosstab or summary grid table...

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...to a table with Column Comparisons based on Independent Samples Column Means and Proportions tests:

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This rule is also designed to mimic those in introductory statistics courses and in SPSS Custom Tables.

 

Requirements

A table with rows and columns.

 

Method

1. Select your table.

2. Go to Properties > RULES on the object inspector.

3. To apply the rule, select the Plus (+) > Browse Online Library > Significance Testing in Tables > Independent Samples Column Means and Proportions Tests.

4. OPTIONAL: By default this rule works on grid-style summary questions, but tick Apply to crosstabs when applicable.

5. OPTIONAL: Tick Apply when Column Comparisons are not shown on the table if you wish to remove the warning which occurs when this statistic is not displayed.

6. OPTIONAL: Tick Set column comparisons to specify which columns of the table should be compared, otherwise leave unticked to compare all columns. When this option is selected, you should enter the names of the columns that you would like to compare in the box provided.

In this example, we are comparing columns B through D to column A, so we use the below format:

A/B,A/C,A/D

7. OPTIONAL: Tick Include settings information in footer.

8. Set the Significance Level (alpha) for lowercase letters, e.g. 0.1 (90%).

9. Set Significance Level (alpha) for uppercase letters, e.g. 0.05 (95%).

10. OPTIONAL: Set Multiple comparison correction.

11. OPTIONAL: Set Numeric data variance assumptions (t-test).

12. OPTIONAL: Set Base used in tests of means.

13. OPTIONAL: Set Proportions test.

14. OPTIONAL: Set Base used in test of proportions.

15. Set the Minimum sample size in a column to include in testing.

16. OPTIONAL: Enter the names of Columns to ignore from testing, one per box.

17. Press OK.

18. Select Column Comparisons in the object inspector via Inputs > STATISTICS > Cells.

 

Please note the following:

  • This rule works by over-riding/ignoring settings and safe-guards built into Displayr. Many of the settings that are over-ridden are designed to protect users from problems in their data, so when applying this rule a higher degree of diligence is required in checking results.
  • This rule over-rides the settings under Properties > APPEARANCE > Significance > Advanced. 
  • In various situations, the formulas used for computing significance in this rule may give incorrect/misleading results (e.g., when the assumption of independence is inappropriate and when the various tests selected are wrong).
  • Effective sample size is computed as Effective Sample Size * Weighted Column Sample Size / Weighted Sample Size.
  • When the variable set selected in Rows is a Nominal - Multi, Binary - Grid, or a Numeric - Grid, the sample size used in the test is the Sample Size (or Weighted Sample Size, or Effective Sample Size, otherwise the Column Sample Size (or the Weighted Column Sample Size, or Effective Column Sample Size) is used.
  • Simplified Independent Complex Samples T-Test - Comparing Two Means is used when Numeric data variance assumptions (t-test) is set to Complex samples.
  • Independent Samples T-Test - Unequal Variance is used when Numeric data variance assumptions (t-test) is set to Unequal variance. When this option is selected in conjunction with setting Base used in test of means to Weighted sample size and Multiple comparison correction is set to None, the resulting tests correspond to an an Independent Samples T-Test in SPSS with Equal variances not assumed.
  • Independent Samples T-Test - Equal Variance is used when Numeric data variance assumptions (t-test) is set to Equal variance (categories compared). When this option is selected in conjunction with setting Base used in test of means to Weighted sample size and Multiple comparison correction to None, the resulting tests correspond to an Independent Samples T-Test in SPSS with Equal variances assumed and also to Compare column means (t-tests) with Estimate variance only from the categories compared selected in SPSS Custom Tables, except where the columns are from multiple response questions.
  • Independent Samples T-Test - Pooled Variance is used when Numeric data variance assumptions (t-test) is set to Equal variance (all non-ignored categories). When this option is selected in conjunction with setting Base used in test of means to Weighted sample size and Multiple comparison correction to None, the resulting tests correspond to Compare column means (t-tests) with Estimate variance only from the categories compared not selected in SPSS Custom Tables, except where the columns are from multiple response questions.
  • Simplified Independent Complex Samples T-Test - Comparing Two Proportions is used when Proportions test is set to Complex samples t-test.
  • Independent Samples Z-Test - Comparing Two Proportions (Pooled) is used when Proportions test is set to Pooled z-test. When this option is selected in conjunction with setting Base used in test of proportions to Weighted sample size and Multiple comparison correction is set to None, the resulting tests correspond to Compare column proportions (z-tests) in SPSS Custom Tables.
  • Independent Samples Z-Test - Comparing Two Proportions (Un-Pooled) is used when Proportions test is set to Un-pooled z-test

 

See Also

How to Use Rules in Displayr

How to Apply Multiple Comparison Correction to Statistical Significance Testing

 

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