Tuesday

April 21, 2015

April 21, 2015

Posted by **Rhea** on Saturday, October 23, 2010 at 7:37pm.

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 -
**PsyDAG**, Saturday, October 23, 2010 at 8:38pm14. 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.

statistics - The scores on an economics examination are normally distributed ...

statistics - Scores on a certain test are normally distributed with a variance ...

statistics - Scores on a certain test are normally distributed with a variance ...

business statistics - Your statistics instructor wants you to determine a ...

statistics - In one history class, 34 students took an exam. The mean of the ...

Statistics - Cholesterol levels of adult males are approximately normally ...

statistics - Section 5.3: Normal Distributions: Finding Values Answer the ...

Statistics - Scores on a certain exam are normally distributed with a mean of 78...

statistics - 1-the graduate selection committee wants to select the top 10% of ...

Statistics - Are these statements true or false? 1. The sample mean, the sample ...