Testing differences between groups

HR Analytics: Exploring Employee Data in R

Ben Teusch

HR Analytics Consultant

Comparing two groups

Quantifying the likelihood

The t-test

Use when the variable to compare is continuous

t.test(tenure ~ is_manager, data = survey)

    Welch Two Sample t-test

data:  tenure by is_manager
t = -1.2158, df = 834.19, p-value = 0.2244
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
 -0.34197615  0.08037243
sample estimates:
mean in group Non-manager mean in group Manager 
                 7.376555            7.507357

The chi-squared test

Use when the variable to compare is categorical

chisq.test(survey$left_company, survey$is_manager)

    Pearson's Chi-squared test with Yates' continuity correction

data:  survey$left_company and survey$is_manager
X-squared = 26.275, df = 1, p-value = 1.97e-06

Where are the formulas?

Let's practice!

HR Analytics: Exploring Employee Data in R