00:01
Hi, i'm david and i'm here to have you answering your question.
00:03
In the question here, we are going to discuss about the assembly distribution of the sample mean.
00:08
By the central limit theorem, it says that if the n -quieter equal to the 30, then the sample mean x -par will be approximately to the normal, in such a way that the mean of the x -bar equal to the mean in the population, standard division x -bar equal to the sigma of the square of n.
00:27
And because it follows by the normal, it will turn the x -bar xxxx we minus the mean over standard deviation.
00:33
We obtain the standard normal.
00:35
In the question here, we're given the x that followed by the normal.
00:39
With the mean, it will equal to the 8 .4, and the standard division equal to the 4.
00:49
He will given the n equal to 100, so it's greater than 30 already.
00:53
In the question a, ask not you find the x bar with the mean.
00:57
So the mean by the formula just equal to the mule and equal to the 8 .4, standard division x par by the formula here, equal to the sigma over square of n, equal to the 4 over square root of the hundred, equal to the 4 over 10, and equal to the 0 .4.
01:16
And i see you got the answer correctly, so good job for your work.
01:20
Now for the question b, want to find the probability that the sample mean x par will be less than the 9 .40.
01:29
Now to find this probability, i need to convert the xxpang to the z.
01:33
To do it, i need to apply this formula here.
01:36
So i will turn the 9 .40 and minus the mean 8 .4 divided by the standard division 0 .4...