Question

hey y'all me again :p

So ...

at a high school, the average grade for the english 10 provincial is 64, with a standard deviation of 10. If 20 students scored between 73 and 86 on the exam, how many students took the exam? Use z-score in your solution.

thanks :)

Answer 1

First convert each raw score to a z-score

So convert x = 73 to a z-score

z = (x - mu)/(sigma)

z = (73 - 64)/(10)

z = 0.9

and then convert x = 86 to a z-score

z = (x - mu)/(sigma)

z = (86 - 64)/(10)

z = 2.2


So the raw scores of 73 and 86 convert to the z-scores 0.9 and 2.2 respectively

Answer 2

You're then told that "20 students scored between 73 and 86 on the exam"

So 20 students have a z-score between 0.9 and 2.2

Answer 3

Your task is to find the area under the standard normal curve from z = 0.9 to z = 2.2


Let's call this area p.


If x students total took the test, then xp students scored between z = 0.9 and z = 2.2


Put another way, if x students total took the test, then xp students scored between 73 and 86

Answer 4

But we know that 20 students scored between 73 and 86, so

xp = 20

Answer 5

So all you need to do is find p. Once you have p, solve for x to get your answer.

Answer 6

is p then .170 ?

Answer 7

you got it

Answer 8

okay so 118 students took the test ?

Answer 9

yes if you round up

Answer 10

thank u so so much

Answer 11

i was so lost, thanks

Answer 12

you're welcome

Answer 13

how did you find that p equaled 170?