Question

@Hero @wio
The scores for a standardized reading test are found to be normally distributed with a mean of 500 and a standard deviation of 50. If the test is given to 500 students, how many are expected to have scores between 500 and 600?

Answer 1

a. 255
b. 171
c. 340
d. 239

Answer 2

@Hero

Answer 3

Do you have a standard normal distribution table available?

Answer 4

If you don't have a table you can use the table here:
http://lilt.ilstu.edu/dasacke/eco148/ztable.htm
The z-score for 600 is 2, the reason being that 600 is 2 standard deviations above the mean. The z-score for 500 is 0, the reason being that 500 is the mean.
Can you use the table to look up the cumulative probabilities for 2.00 and 0.00 and post the result?

Answer 5

Thank you so much!

Answer 6

.5080 I think!

Answer 7

I mean .9772

Answer 8

Good work!
0.9772 is the z-score for 600. The z-score for 500 is 0.500. The expected number with scores between 500 and 600 is found from:
\[500\times(0.9772-0.5000)=you\ can\ calculate\]

Answer 9

Thank you so much! =)
Im calculating

Answer 10

238.6 : )

Answer 11

Correct! So, when you round up, you have found the correct choice of answer :)

Answer 12

Thank you I really appreciate the help!!!

Answer 13

You're welcome :)