CW4

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Load data/check data

data(sleep)
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 ...

see the distribution

library(lattice)
densityplot( ~ extra, 
             groups = group,
             data = sleep,
             auto.key = TRUE,
             lty = c(1, 2),
             plot.points = F,
             type = "g",
             xlab = "Sleeping time",
             main = "Sleeping time dirfference between w/& w/o treatment")

run t.test

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

Due to t < 2, and p-value > 0.05, there’s no signifigance thus I can’t support my null my hypothesis, but 95 percent confidence interval included 0 so I can’t completely deny my null hypothesis