1. Is there a difference in satisfaction level between those that left and those that stayed in the company?

Employees that stayed, on average are more satisfied

## 
##  Welch Two Sample t-test
## 
## data:  HR$satisfaction_level by HR$left
## t = 46.636, df = 5167, p-value < 2.2e-16
## alternative hypothesis: true difference in means between group 0 and group 1 is not equal to 0
## 95 percent confidence interval:
##  0.2171815 0.2362417
## sample estimates:
## mean in group 0 mean in group 1 
##       0.6668096       0.4400980

2. Is there a difference in average monthly hours between those that left and those that stayed in the company?

People that left, on average, worked more hours

## 
##  Welch Two Sample t-test
## 
## data:  HR$average_montly_hours by HR$left
## t = -7.5323, df = 4875.1, p-value = 5.907e-14
## alternative hypothesis: true difference in means between group 0 and group 1 is not equal to 0
## 95 percent confidence interval:
##  -10.534631  -6.183384
## sample estimates:
## mean in group 0 mean in group 1 
##        199.0602        207.4192

3. Is there a difference in last evaluation between those that left and those that stayed in the company?

There is no difference in employees’ last evaluation, between those that left and those that stayed.

## 
##  Welch Two Sample t-test
## 
## data:  HR$last_evaluation by HR$left
## t = -0.72534, df = 5154.9, p-value = 0.4683
## alternative hypothesis: true difference in means between group 0 and group 1 is not equal to 0
## 95 percent confidence interval:
##  -0.009772224  0.004493874
## sample estimates:
## mean in group 0 mean in group 1 
##       0.7154734       0.7181126