Excercie CW4

data("sleep")

library(lattice)

## Warning: 套件 'lattice' 是用 R 版本 4.1.3 來建造的

head(sleep)

##   extra group ID
## 1   0.7     1  1
## 2  -1.6     1  2
## 3  -0.2     1  3
## 4  -1.2     1  4
## 5  -0.1     1  5
## 6   3.4     1  6

str(sleep)

## 'data.frame':    20 obs. of  3 variables:
##  $ extra: num  0.7 -1.6 -0.2 -1.2 -0.1 3.4 3.7 0.8 0 2 ...
##  $ group: Factor w/ 2 levels "1","2": 1 1 1 1 1 1 1 1 1 1 ...
##  $ ID   : Factor w/ 10 levels "1","2","3","4",..: 1 2 3 4 5 6 7 8 9 10 ...

畫出兩組的boxplot圖

group1=控制組 ; group2=實驗組

boxplot(extra ~ group, data = sleep)

看出控制組和實驗組的extra scores的分布有差距

因此假設H0:控制組與實驗組的extra scores沒有差異;H1:控制組與實驗組的extra scores有差異

做控制組與實驗組extra scores的T檢定

t.test(extra ~ group, data = sleep)

## 
##  Welch Two Sample t-test
## 
## data:  extra by group
## t = -1.8608, df = 17.776, p-value = 0.07939
## alternative hypothesis: true difference in means between group 1 and group 2 is not equal to 0
## 95 percent confidence interval:
##  -3.3654832  0.2054832
## sample estimates:
## mean in group 1 mean in group 2 
##            0.75            2.33

此結果顯示無法拒絕虛無假設，表示兩組extra scores無差異，因為p-value>0.05 ; 信賴區間包含0 ; t=1.86<2。