Statistical significance testing

Undertake a paired t-test or Wilcoxon signed rank test to test for differences between means (or medians) of paired numeric values.

# Paired t-test or Wilcoxon signed rank test on numeric data

Undertake a paired t-test or Wilcoxon signed rank test to test for differences between means (or medians) of paired numeric values.

Inputs are:

- - the type of test desired (paired t-test or Wilcoxon signed rank);
- - desired level of confidence for confidence interval estimation;
- - the desired number of digits after the decimal point in summary results; and
- - two columns of data (including a header row with labels for each column). The data must be paired in rows (ie each row is a pair of corresponding measurements) and the columns must be the same length.

**Note** missing values in the data will be omitted from calculations.

For this analysis, the values in the first column are subtracted from the corresponding values in the second column and a t-test (or signed rank test) undertaken to test for deviation of the mean (median) difference from zero.

Outputs include:

- - a summary of statistical test results for the selected test, including 2-tailed and 1-tailed for both tails;
- - Shapiro-Wilk test for normality on both sets of measurements and the differences;
- -
**Note:**for groups with < 4 or > 5000 observations it is not possible to calculate Shapiro-Wilks W statistic to test for normality of distribution; - - a numeric summary of the data for each measurement and the difference, including histograms and normal plots;
- -
**Note:**for groups with only one observation or with standard deviation = 0 histograms and quantile plots are not shown; and - - boxplots of the data by group and a plot of confidence intervals about the mean (or median) value for each group.

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