1. T Test of Average Monthly Hours by Left

## 
##  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 Stayed and group Left is not equal to 0
## 95 percent confidence interval:
##  -10.534631  -6.183384
## sample estimates:
## mean in group Stayed   mean in group Left 
##             199.0602             207.4192

p-value interpretation: We reject the null hypothesis since the p-value is less than 0.01 and conclude that there is a significant difference between the mean average monthly hours of employees that left versus stayed.

t-test interpretation: The difference in mean average monthly hours between employees that left versus stayed is significant where the difference is at least 6.18 hours.

non-technical interpretation: Employees that worked more hours left.

Plot:

2. T Test of Satisfaction Level by Left

## 
##  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 Stayed and group Left is not equal to 0
## 95 percent confidence interval:
##  0.2171815 0.2362417
## sample estimates:
## mean in group Stayed   mean in group Left 
##            0.6668096            0.4400980

p-value interpretation: We reject the null hypothesis since the p-value is less than 0.01 and conclude that there is a signiciant difference between the mean satisfaction levels of employees that left versus stayed.

t-test interpretation: The difference in mean satisfaction level between employees that left versus stayed is significant where the difference is at least 21.7 points lower for employees that left.

non-technical interpretation: Employees that had a lower satisfaction level left.

Plot:

3. T Test of Last Evaluation Score by Left

## 
##  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 Stayed and group Left is not equal to 0
## 95 percent confidence interval:
##  -0.009772224  0.004493874
## sample estimates:
## mean in group Stayed   mean in group Left 
##            0.7154734            0.7181126

p-value interpretation: We fail to the reject the null hypothesis since the p-value is greater than 0.01 and conclude that there is not a significant difference in the last evaluation for employees that left versus stayed.

t-score interpretation: The difference in mean last evaluation score between employees that left versus stayed is insignificant where the difference is only at least 0.4 points.

non-technical interpretation: Employees that left and stayed had similar last evaluation scores.

Plot:

4. T Test of Number of Projects by Left

## 
##  Welch Two Sample t-test
## 
## data:  hr$number_project by hr$left
## t = -2.1663, df = 4236.5, p-value = 0.03034
## alternative hypothesis: true difference in means between group Stayed and group Left is not equal to 0
## 95 percent confidence interval:
##  -0.131136535 -0.006540119
## sample estimates:
## mean in group Stayed   mean in group Left 
##             3.786664             3.855503

p-value interpretation: We fail to the reject the null hypothesis since the p-value is greater than 0.01 and conclude that there is not a significant difference in the number of projects for employees that left versus stayed.

t-score interpretation: The difference in mean number of projects between employees that left versus stayed is insignificant where the difference is only at least 0.065 projects.

non-technical interpretation: Employees that left and stayed had a similar number of projects.

Plot: