Clouds were randomly seeded or not with silver nitrate. Rainfall amounts were recorded from the clouds. The purpose of the experiment was to determine if cloud seeding increases rainfall.
The rainfall distributions are more nearly symmetric after a log transformation. The log transformation also makes the variance of the two groups more nearly equal.
After a log transformation, a pooled t-test may be appropriate. (Without a transformation it is neither appropriate (failing both the normality and equal variance assumptions) nor significant at .05.) Without transforming, a Mann-Whitney U test would be appropriate.
A boxplot or the dotplot of rainfall for the two groups of clouds is helpful.