t-test of MPG by Transmission
##
## Welch Two Sample t-test
##
## data: cars1$mpg by cars1$am_char
## t = -3.7671, df = 18.332, p-value = 0.001374
## alternative hypothesis: true difference in means between group Automatic and group Manual is not equal to 0
## 95 percent confidence interval:
## -11.280194 -3.209684
## sample estimates:
## mean in group Automatic mean in group Manual
## 17.14737 24.39231
##
## Welch Two Sample t-test
##
## data: cars1$gear by cars1$am_char
## t = -6.8995, df = 22.568, p-value = 5.462e-07
## alternative hypothesis: true difference in means between group Automatic and group Manual is not equal to 0
## 95 percent confidence interval:
## -1.5264836 -0.8216945
## sample estimates:
## mean in group Automatic mean in group Manual
## 3.210526 4.384615
Conclusion: Manual cars get better MPG than automatic