00:01
So now we're looking at finding a confidence interval for a mean, and we're told that the sample size is 24.
00:10
We're told that the mean of those 24 numbers came to a 41 .6 decibels.
00:19
And we know that the standard deviation, and it sounds like the standard deviation is for those 24 rooms, so that is a sample standard deviation with 7 .5 decibels.
00:35
And we want to find a 95 % confidence interval for the mean, for the true mean sound level in decibels.
00:47
And so we know that this is a small sample.
00:50
So we're going to use our t star value.
00:55
And we'll have s over the square root of n.
00:58
So we know that the 41 .6 is our x bar.
01:04
And then if we have sample size of 24, we know that our degrees of freedom is 23.
01:12
And so if we look on our table and we look for the degrees of freedom here for 23, and then look for the level of confidence to be 95%.
01:21
And that value we get here, if i looked it upright, is 2 .06.
01:28
And then we have our sample standard deviation of 7 .5 and we have our sample size of 24...