00:01
So in this question, the given mean value, i'll just write them, which is denoted by me, that is 8 .4, and the standard division, which is right.
00:11
Standard division, which is given as 2 .7, and the n is given as 45.
00:16
So from the central limit of the theorem, so the n, which is 45, is greater than 30.
00:22
So we can use the normal distribution here, normal distribution.
00:27
So let's say x be the random variable.
00:31
For this one, this is normally distributed, 8 .4 and 2 .7.
00:36
So in part a, what we have to find? we have to find between 8 and 9 hours.
00:44
So more than 8 hours per week.
00:47
So the probability of x is greater than 8.
00:51
So what that means, let me just graph the normal distribution first.
00:55
This is the mean value, 8 .4.
00:57
So the 8 is over here.
00:59
So we need to get the area of this region, which is equal to we can use the normal cdf function of the calculator.
01:05
The lower boundary is 8.
01:07
There is no upper boundary that goes to positive infinity.
01:10
So we have to put a greater number.
01:12
Let's write 1e99.
01:14
This is a great big number.
01:17
And the mean value here is 8 .4 and the standard deviation 2 .7.
01:22
Let's get the second distribution...