Data with skewed distribution were presented as the median (Q[sub]1, Q[sub]3) and compared by the Wilcoxon rank-sum test
We used the Mann-Whitney U test or Wilcoxon rank-sum test
(Hart, 2001) which is a non-parametric alternative test to the independent sample t-test.
66 that an observation in group one (the acetaminophen and opioid combination group) was less than an observation in group two (the opioid only group) using a Wilcoxon rank-sum test
Neither log-rank nor Wilcoxon rank-sum tests
assume any particular distribution of the survivor curve, and where the log-rank test places more weight on later survival times, the Wilcoxon rank-sum test
places more weight on early survival times.
Continuous parameters were presented as mean +- standard deviation and compared using the student's t test or Wilcoxon rank-sum test
, as appropriate.
Data were not normally distributed; therefore, we used the Wilcoxon rank-sum test
for all analyses (Zar, 2010).
Wilcoxon Rank-sum test
was used to compare repeated measurements on a single sample to assess whether their mean population ranks differ.
For statistical analysis, we report one-tailed Wilcoxon rank-sum test
as the data of our study does not come from a population with a normal distribution.
The Wilcoxon signed-ranks test was superior to the Wilcoxon rank-sum test
for paired data, while the modified t test on ranks was slightly superior to both.
The results for the patient survey were analyzed using the Wilcoxon rank-sum test
Therefore, the Wilcoxon rank-sum test
, a nonparametric test for assessing whether two samples of observations come from the same distribution, was used to evaluate the data sets.
Differences between groups were compared using the [chi square] test for categorical variables and the Wilcoxon rank-sum test
for continuous variables.