The first step in a Wilcoxon rank sum test is to combine the data values in the two samples and assign a rank of 1 to the:

A) smallest observation
B) middle observation
C) largest observation
D) observation that occurs most frequently
E) observation that occurs least frequently

The first step in a Wilcoxon rank sum test is to combine the data values in the two samples and assign a rank of 1 to the smallest observation. This is because the Wilcoxon rank sum test is a non-parametric test that compares the medians of two independent samples, and assigning the smallest observation a rank of 1 ensures that the smallest value in each sample is directly compared.