00:01
Okay, so this question is asking us to find the 90 % confidence interval.
00:05
So we need to start by finding the sample mean.
00:10
Um, it gives you like the means for each sample, but we want to find overall.
00:17
So what you're going to do is take the mean from each sample and if you add, they give us the number of people in each sample.
00:28
If you add that up, that will give you the total number of people.
00:32
So what we want to do is take the mean, so for example, for sample 65 .1 and we're going to take that times, um, for example, the 23 divided by 125 because we want to know what percentage of the total this mean is.
00:55
Okay, so we're going to take that times 0 .184.
00:57
Okay, our next mean is 65 .21.
01:03
We are going to take that, multiply it times, write our second amount of people, divide by the total, so 0 .192.
01:18
Okay, and we're just going to keep doing this, so 65 .3 times 0 .2.
01:26
Okay, plus 65 .4 times 0 .208 plus 65 .5 times 0 .208.
01:41
0 .16, sorry that cut off.
01:50
Okay, you can just put those onto your calculator, see what you get out.
01:55
Um, looks like i got 65 .308.
02:01
Okay, now we want to do the same thing with our standard deviation.
02:08
We want to find the total out of all those samples, what our mean is.
02:12
So you can take those same percentages, just times different standard deviations, so times 0 .184.
02:20
For the first one, times 0 .192 plus 5 .3 times 0 .2 plus 5 .2 times 0 .208 plus 5 .1 times 0 .216.
02:41
Okay, again, add all those up, you should get for overall standard deviation 5 .292.
02:53
Alright, um, next thing is we want to write down our total number of people, so if you add up the number of people from each sample, we get 125.
03:08
Okay, next part we're gonna do, so we are looking for 90 % confidence interval...