Table 1. Statistical tests performed and programs used for each objective.

Objectives	Tests (a = 0.05)	Programs*
Determine the behavior of the prevalence over the years.	Simple linear regression	SPSS
Compare the prevalence of disease between the genders.	Pearson’s Chi-square	R
Compare the patients ages between the genders.	Mann-Whitney U	SPSS
Compare ethnic proportion of cases of pityriasis versicolor with the sample proportion and determine which ethnic groups are responsible for the statistical difference.	Chi-square/Chi-square corrected by Bonferroni	WinPEPI

* SPSS version 18, R version 13.2 and WinPEPI version 11.25.