00:01
In this question, there is a sample and the sample of 30 rings.
00:05
That means the sample size is given us 30 rings.
00:10
And the standard division, so the standard division of the sample, which is given us 20 milliliters.
00:17
And the average, so this is the mean value for the sample, which is x bar, that is equal to 307.
00:24
And the 95 confidence interval.
00:27
So the confidence level.
00:30
Confidence level, which is denoted as 95%, which is 0 .95 here.
00:38
So first of all, the sample size is 30 if the sample size is more than 30 or equal to 30.
00:45
So we have to use the z distribution here.
00:47
Let me just write the formula for the confidence interval, which is equal to this is x bar plus or minus z alpha over two times, the population standard deviation, and divided by the square of the sample size, which is n here.
01:06
So in this case, so actually for this distribution, the population standard division is given as 20 here.
01:13
So i can write not as.
01:15
I'm going to use the leather sigma here.
01:18
So i'm going to just use a sigma here...