Post a New Question

Statistics - M/C

posted by .

14.
The marks on a statistics test are normally distributed with a mean of 62 and a variance of 225. If the instructor wishes to assign B’s or higher to the top 30% of the students in the class, what mark is required to get a B or higher?

a. 68.7 b. 71.5 c. 73.2 d. 74.6 e.69.9

The answer is E, but don't know why.



2. Suppose the test scores of 600 students are normally distributed with a mean of 76 and variance
of 64. The number of students scoring between 70 and 82 is:

a. 272 b. 164 c. 260 d. 136 e. 328

The answer is E but don't know why.

  • Statistics - M/C -

    14. Variance = SD^2

    Z = (score-mean)/SD = (score-62)/15

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion (.30) to give you the Z score. Put that value in the above equation to find the score.

    Z = ([70 or 82]-76)/8

    Use the Z scores in the same table to find the proportions between them and multiply by 600.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

More Related Questions

Post a New Question