Math Is Fun Forum

babyangel1972

Member

Registered: 2005-12-12

Posts: 18

Help...

Let's say a student scored 45 on a math achievement test for which the mean was 36 and the standard deviation was 6.  Judging on the basis of this performance, what score would you predict for her on a standardized test for which the mean is 100 and the standard deviation 15?

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Help...

45-36=9 he is 9 points above mean.
9/6=1.5 he is 1.5 times of stdev above mean.
And this should always holds, regardless of the value of mean or stdev.
Why?
Suppose you can add all scores with 2 points, his will remain 9 points ahead.
Suppose you can multiply all scores by 2, his will be 18 points above mean, still 1.5 times of stdev.

Suppose he does as well as in the former test, he will still get a score 1.5 times of stdev above mean. This time, mean=100, stdev=15, he will get 122 or 123.

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X'(y-Xβ)=0

babyangel1972

Member

Registered: 2005-12-12

Posts: 18

Re: Help...

Thank You!

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Help...

You are welcome

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X'(y-Xβ)=0

brodr7630

Member

Registered: 2013-01-27

Posts: 1

Re: Help...

Let's say a student scored 45 on a math achievement test for which the mean was 36 and the standard deviation was 6. Judging on the basis of this performance, what score would you predict for her on a standardized test for which the mean is 100 and the standard deviation 15?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,646

Re: Help...

Look at post #2.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob