title: “Exercise 11” author: “Airah Kenzky” date: “2023-05-01” output: html_document —

1.1 What is the mean and standard deviation of mpg of the mtcars data?

## [1] 20.09062

## [1] 6.026948

1.2 Is there suficient evidence that the population mean score of the mtcars data exceeds 19 miles per gallon?

## 
##  One Sample t-test
## 
## data:  mtcars$mpg
## t = 1.0237, df = 31, p-value = 0.157
## alternative hypothesis: true mean is greater than 19
## 95 percent confidence interval:
##  18.28418      Inf
## sample estimates:
## mean of x 
##  20.09062

1.3 Refer to Question 1.2, state your null and alternative hypotheses?

Null Hypothesis: The population mean score of the mtcars data doesn’t exceeds 19 miles per gallon.

Alternative Hypothesis: The population mean score of the mtcars data exceeds 19 miles per gallon.

1.4 Is there sufficient evidence that mean difference of miles per gallon beween automatic and manual cars differ statistically?

## 
##  Welch Two Sample t-test
## 
## data:  mpg.at and mpg.mt
## t = -3.7671, df = 18.332, p-value = 0.001374
## alternative hypothesis: true difference in means is not equal to 0
## 95 percent confidence interval:
##  -11.280194  -3.209684
## sample estimates:
## mean of x mean of y 
##  17.14737  24.39231

1.5 Refer to Question 1.4, state null and alternative hypotheses?

Null Hypothesis:There’s no mean difference of miles per gallon between automatic and manual cars.

Alternative hypothesis: There’s mean difference of miles per gallon between automatic and manual cars.