Question

the mean of test scores is 500. the standard deviation is 100. what is the score cut off for the top 10% of scores?

Answer 1

is it with normal distribution?

Answer 2

yes

Answer 3

there!

Answer 4

lol.... thnx :)

Answer 5

the top 10% are above the 90th percentile then right?

Answer 6

so out of the choices 525, 628, 755 and 663, what would be the cutoff score

Answer 7

yes, I think so.

Answer 8

i wish I new our range ....

Answer 9

they didn't give it.

Answer 10

yeah..... gonna have ta try it out the long way lol

Answer 11

i wanna say 663 but i cant be sure of that

Answer 12

okay. how did you get what you think is the answer?

Answer 13

the empirical rule is that 68% are within 1sd

95% are within 2sd

and 98.7 is at 3sd

90% falls under between 600 and 700

Answer 14

663 just feels to fit the bill better; but i cant say for certainity

Answer 15

okay, thank you

Answer 16

this might be late but i was bound to get a right answer for you :)

Answer 17

the correct answer is 628; and why?

I had to ask my stats teacher and he showed me how to use the z-table.

We are looking for amount of area that is 90% under the normal distribution- (1-.1 = .9)

teh z-table in my book measures from the mean itself so we have to -.5 to get the right numbers...

.9-.5 = .4

i find the value that is closest to, but under .4

Answer 18

that value is the intersection of '1.2' and '.08'. this is amount of 'deviation' we use to calculate with:


1.28(100) = 128 <- deviation from the mean
^^ ^^
^^ our given 'sd'
^^
out z-table findings

500 + 128 = 628.