# R, t-test

```> sleep
> sleep_wide <- data.frame(
ID=1:10,
group1=sleep\$extra[1:10],
group2=sleep\$extra[11:20]
)

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

ID group1 group2
1  1  0.7  1.9
2  2 -1.6  0.8
3  3 -0.2  1.1
4  4 -1.2  0.1
5  5 -0.1 -0.1
6  6  3.4  4.4

> t.test(extra ~ group, 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

> t.test(extra ~ group, sleep, var.equal=TRUE)

Two Sample t-test

data: extra by group
t = -1.8608, df = 18, p-value = 0.07919
alternative hypothesis: true difference in means between group 1 and group 2 is not equal to 0
95 percent confidence interval:
-3.363874 0.203874
sample estimates: mean in group 1 mean in group 2
0.75            2.33

> t.test(sleep_wide\$group1, sleep_wide\$group2)

Welch Two Sample t-test

data: sleep_wide\$group1 and sleep_wide\$group2
t = -1.8608, df = 17.776, p-value = 0.07939
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
-3.3654832 0.2054832
sample estimates:
mean of x mean of y
0.75      2.33

> t.test(extra ~ group, sleep, paired=TRUE)

Paired t-test

data: extra by group
t = -4.0621, df = 9, p-value = 0.002833
alternative hypothesis: true mean difference is not equal to 0
95 percent confidence interval:
-2.4598858 -0.7001142
sample estimates:
mean difference
-1.58

> t.test(sleep\$extra, mu=0)

One Sample t-test

data: sleep\$extra
t = 3.413, df = 19, p-value = 0.002918
alternative hypothesis: true mean is not equal to 0
95 percent confidence interval:
0.5955845 2.4844155
sample estimates: mean of x
1.54

```