Comparison of independent samples

Command:

Statistics Create tables Comparison of independent samples

Description

This procedure allows to create a publication-ready table showing comparison of subgroups in multiple variables.

Required input

• Variables: select the variables of interest in the top left box and next click the right arrow button to move the selection to the Selected variables list.
• Categorical variable to define subgroups: a categorical variable that will be used to break-up the data into several subgroups that will be compared.

• Filter: a filter can be sued to include only a selected group of cases in the results.

Options

• Statistics: select the statistics to be displayed in the table.
  • Sample size
  • Choose Mean or Median and a measure of variability.
    • For mean, this can be the 95% Confidence Interval of the mean, the sample Variance, Standard Deviation, or the Standard Error of the mean. The Variance, Standard Deviation of Standard Error of the mean can optionally be preceded by a ± sign (although this is not recommended).
    • For the Median, this can be the 95% Confidence Interval of the median, or a percentile range (2.5-97.5, 5-95, 10-90, 25-75).
• For statistical tests, select parametric tests for non-parametric tests.
  • When parametric tests are selected, MedCalc will perform a t-test when there are 2 groups, or ANOVA (with an optional Tukey-Kramer or Scheffé post-hoc test) when there are more than 2 groups.
  • When non-parametric tests are selected, MedCalc will perform a Mann-Whitney test when there are 2 groups, or a Kruskal-Wallis test (with an optional post-hoc test according to Conover or Dunn) when there are more then 2 groups.
  • When the post-hoc test is significant, differences between groups will be indicated with characters a..z. When the option "Use superscripts to indicate differences" is selected the character a..z is placed in superscript next to the mean or median, otherwise it is placed below the group's statistics (like in the example below). Groups with the same letter differ significantly in the post-hoc test.
  • For categorical variables, MedCalc will always use a Chi-squared test. See Edit variables list and Variable properties to indicate which variables are categorical.

Results

The program creates a table with the results of the selected test for each variable.

See also

• Independent samples t-test: computational notes
• Export results to Microsoft Word
• How to define and use labels for the different categories of a variable
• Comparison of paired samples