Question

In: Statistics and Probability

The average math SAT score is 521 with a standard deviation of 114. A particular high...

The average math SAT score is 521 with a standard deviation of 114. A particular high school claims that its students have unusually high math SAT scores. A random sample of 60 students from this school was​ selected, and the mean math SAT score was 538. Is the high school justified in its​ claim? Explain.

answers is ( choose yes/or no) , because the z score ( which is? ) is ( choose, usual or not usual) since it ( choose, does not lie ,or lies) within the range of a usual event , namely within ( choose 1, 2 or 3 standard deviations) of the mean of the sample means. round to two decimal places as needed

Solutions

Expert Solution

Let X be the SAT score of any given student. X has a mean and standard deviation

Note that we do not know the distribution of X

Let be the sample means of a randomly selected sample of n=60 students. Since the sample size is greater than 30, using the central limit theorem (CLT), we can say that has a normal distribution with mean and standard deviation (also called standard error of mean)

A random sample of size 60 selected from this particular school has a mean SAT score of 538.

The z score of 538 is

We can see that any random sample of 60 students would have a sample mean SAT score of 521 with SD 14.7173. This particular school had a sample mean of 538 which is 1.16 standard deviation from the mean. We say that a value which is more than 2 standard deviations from the mean is unusual. Hence this score is not unusual.

Is the high school justified in its​ claim that its students have unusually high math SAT scores?

ans: No, because the z score 1.16 is not usual since it lies within the range of a usual event , namely within 2 standard deviations of the mean of the sample means.


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