Question

Can anyone help me with this question:

Form B has a mean of 150 and David performed 2.5 standard deviation below the mean. What score did David have?

Answer 1

your zscore is 2.5

Answer 2

since it is below the mean, the ztables answer should be less than .5

Answer 3

no, i got 60

Answer 4

what does "no i got 60" mean?

Answer 5

how did you 60?

Answer 6

\[z=\frac{x-\bar x }{sd}\]

Answer 7

\[-2.5=\frac{x-150 }{sd}\]

Answer 8

i think we would need a standard deviation to begin with

Answer 9

there are many normal distributions, which i am assuming this to be; that have a mean of 150 .... so the sd is important as a ruler to measure against

Answer 10

@amistre64 it means i some how got 60..duhh

Answer 11

can you explain how?

Answer 12

"i got 60" has no study value to it what so ever.

Answer 13

i divided 150 by 2.5..but hay i could be wrong.

Answer 14

oh, well that is a method :) i dunno how accurate it would be either tho

Answer 15

MEwing, is there any information that you might be excluding from this?

Answer 16

Nope, but I feel like there is. I will type all the questions, see if that helps. this should not be so hard to figure out but it is for some reason!

Answer 17

Samuel, a teacher in middle school, created two forms of the final exam for his students. He distributed them equally to the class.
You task is to help Samuel solve the following questions using the following formula related to standard error of measurement (SEM), standard deviation (SD), and reliability of the test. (Show all you computational work)

SEM = SD * squared root of (1-reliability)


1. Form A of the final exam has a standard deviation of 20 and a reliability of .75. What is the standard error of measurement for Form A?
Answer: 20√1-.75 SEM=0.25

2. A student, Susan, had a score of 83 on Form A. What does her true score fall at a 95% confidence level?
Answer: 83 plus/minus 2*3 = the true score is between 77-89
3. Form B has a standard error of measurement of 6 with a reliability of 0.84. What is the standard deviation for Form B?
4. Form B has a mean of 150 and Josh performed 1 standard deviation above the mean. What score did Josh have on Form B?
5. Again, Form B has a mean of 150 and David performed 2.5 standard deviation below the mean. What score did David have?

Answer 18

oh, so the sd is what we found found the last question :)

Answer 19

or its related to it right?

Answer 20

sd = 15 if i recall correctly, not that i could verify that to well

Answer 21

-2.5(15) + 150 = x

would be it if the 15 is good

Answer 22

x = 112.5 if it is

Answer 23

which of course aint 60, but you know .... might be right lol

Answer 24

Thanks for all the help tonigh super appreciated!

Answer 25

hope it helped :)