Trimmed means: paired samples test

Command:

Statistics Trimmed means Paired samples test

Description

This procedure compares the trimmed means of two paired samples.

Use Trimmed Means if you want to maintain the scale of your original data (unlike the Wilcoxon test) while protecting your results from the bias of extreme outliers (unlike the T-test).

Required input

Select the variables for sample 1 and sample 2, and a possible filter for the data pairs. Differences will be calculated as Sample2−Sample1.

Options

• % Trimming: select the percentage of observations that will be trimmed away. For example, when you select 20% then the lowest 20% and highest 20% of observations will be dropped for the calculation of the trimmed mean.
• Confidence interval: select the required confidence interval for the difference between the trimmed means. A 95% confidence interval is the usual selection.

Results

The results windows displays the sample size, arithmetic mean and its 95% confidence interval, followed by the trimmed mean, the trimmed mean sample size and the 95% confidence interval of the trimmed mean for the 2 samples.

Comparison of paired samples

The report shows the difference between the trimmed means with its 95% confidence interval.

Next follow the test statistic t, the Degrees of Freedom (DF) and the two-tailed probability P. When the P-value is less than the conventional 0.05, the null hypothesis is rejected and the conclusion is that the two trimmed means do indeed differ significantly.

See Calculation of Trimmed Mean, SE and confidence interval for computational details.

Literature

• Wilcox RR (2022) Introduction to robust estimation and hypothesis testing. 5^th ed. Elsevier Academic Press.

See also

• Yuen-Welch test for the comparison of 2 independent trimmed means.