00:01
Now here we look at a four little questions.
00:02
First one says all possible samples of sars 20 are taken from population means compute which sample.
00:07
The mean of the sample means for ass is quarter to square to the sample variance, now less than the population mean equal to population mean, of course the correct answer should be c, right? and two says which of the foreign pairs parameter is sufficient to find a specific normal curve? so you just need the mean and the standard duration, right? so that's a.
00:35
Assuming scores on recent national statistics exam are normal disputed with the mean of 74 and standard ratio 6.
00:43
Find probably that the randomness like the student school more than 77 points, right? well, that actually, if you look at the distribution of the score, which i call it x, it's a normal distribution according to the question with the mean of 74, you look at the value 74 and you look at the probability the score more than 77, right? so you look at the air rate to the right of that.
01:07
The air rate is normally called alva.
01:10
So you can find this out of from the z score.
01:12
So the alpha is actually given by 77 minus 74 divided by the same variation, which is six.
01:18
So you get that to be 0 .5, right? so the z squared 0 .5.
01:25
And of course you can look up the alva value from the z table.
01:29
And i found that to be a 30, 30 .85 percent.
01:34
So out of actually is 30 .8 %.
01:44
So that's my probability, right, for this question.
01:49
A random sample of 50 statistics students to select what's probably the mean score of the sample is more than this.
01:55
Well, you know, you look at the mean score of these 50 students, the standard deviation, it has the same mean, which is 74, but the standard variation is reduced by the sample size, right? so the standard version will be given by six divided by square root of the 50, right, the sample size...