00:02
For a 90 % confidence interval, we use a t -distribution with 51 degrees of freedom and how we calculate it? 52 minus 1.
00:25
So the critical value for a 90 % confidence interval level with 51 degrees of freedom is 1 .675.
00:50
So the margin of error is equal to critical value multiplied by sample standard deviation divided by square root of sample size.
01:13
So here we can calculate it as 1 .675 multiplied by 4 .4 divided by square root of 52.
01:23
So here it is equal to 1 .675 multiplied by 0 .609 which is equal to 1 .019.
01:36
So we can say that the 90 % confidence interval is equal to sample mean plus minus margin of error is equal to 22 .5 plus minus 1 .019.
02:05
So we can say that it is equal to 21 .48 and 23 .5.
02:11
Now moving to the b part.
02:14
For our 95 % confidence interval, we use a t -distribution with 51 degrees of freedom.
02:21
So the critical value is 2 .009 and here margin of error, we are using the same formula.
02:32
So 2 .009 multiplied by 4 .4 divided by square root of 52...