Though the northernmost islands experience a bit of rain, September is largely dry, warm and sunny throughout the islands. High season in Hawaii doesn't start till mid-December, so September is still off-season for the Hawaii tourism industry and deals abound.
T-tests and analysis of variance (ANOVA) are widely used statistical methods to compare group means. For example, the independent sample t-test enables you to compare annual personal income between rural and urban areas and examine the difference in the grade point average (GPA) between male and female students.
Measures of effect size in ANOVA are measures of the degree of association between and effect (e.g., a main effect, an interaction, a linear contrast) and the dependent variable. They can be thought of as the correlation between an effect and the dependent variable.