00:02
Hello, so with this information, we can go ahead and find the degree of freedom, which is n -1, which is 56 minus 1.
00:19
So we got to add 90 % confidence interval.
00:27
We need to first get a t value.
00:29
So we want to get a t value at alpha over 2 and the degree of freedom.
00:36
We already have the degree of freedom to be 55.
00:40
Let's talk about alpha or over 2.
00:41
So alpha is 1 minus confidence anymore.
00:47
So that's 1 minus 0 .9.
00:52
So you've got 0 .1.
00:55
So alpha over 2 will be 0 .05.
01:00
So from the t table, we need a t value at 0 .05.
01:07
The degree of freedom of 55.
01:16
So from the t -table, a good approximation is going to be, let's see, that's going to be 1 .6 .71.
01:35
That's 1 .6 .71.
01:37
So once we have this, we can find the margin of error.
01:43
So let's find the margin of error.
01:49
That is given by the t value times s over the square root of n so it's 1 .6 .71 s is the standard division which is uh 4 .4 divided by the square root of n which is 56.
02:18
So let's try that.
02:24
So we got 1 .671 times divided by square root of 56 .56.
02:37
Is going to be 0 .983.
02:45
Okay.
02:48
So our confidence interval, another 90 % confidence interval, is going to be x minus moe, then x, that's x bad as the mean, plus moe.
03:07
Okay? so we have, what is our mean? it is 22 .5.
03:16
We have 22 .5 minus 0 .983 and then 22 .5 plus 0 .983.
03:33
Okay, so 22 .5 minus .3.
03:39
Then we're going to have 21 .517.
03:48
Then we add them up.
03:55
We'll get 23 .483.
04:00
Or we can write that as let's just go back to the question.
04:12
Okay, yeah.
04:13
So this is just from this to that.
04:17
So that's between these two values.
04:20
Let's look at bb is at 95.
04:25
Yeah, yeah.
04:27
That's 95 % confidence in a month.
04:32
So we're going to go to the same procedure...