ATAR Notes: Forum
VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE General & Further Mathematics => Topic started by: Blonk on November 03, 2011, 07:25:41 pm
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I have 2 questions that I have no idea how to figure out because I didnt pay attention in class.
1. A student's standard mark on a class test is z= -2.1.
On the basis of this score, and assuming the test marks follow a normal distribution, it can be concluded that his test mark
was:
A: in the bottom 2.5% of marks in the class.
B: in the bottom 5% of marks in the class.
C: in the bottom 16% of marks in the class.
D: in the top 5% of marks in the class.
E: in the top 2.5% of marks in the class.
2. A student's standardised mark on a class test was z= -1.7. The mean mark for the class is 55 and the standard deviation is
2.85.
Their mark on the test was closest to:
A: 49
B: 50
C: 53
D: 58
E: 60
If anyone is able to give me the answers for these 2 questions and provide some form of working out or how to work it out on the ClassPad calculator, please help me out!
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z score indicates how many standard deviation it is from the mean in that case it is 2 (2.1) standard deviation. since it's negative it means it's below the mean so bottom 2.5%
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for Q2) use algebra for the formula to work out z-score:
so: z-score = x-value - Mean
------------------------
S.d
Sub the z-score, mean and s.d
so
-1.7 = x - 55
---------
2.85
then: 2.85 x -1.7 = x - 55
after you find 2.85 x -1.7 add 55 to it and u should get your answer :D
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woops i mean the student's mark :P
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z score indicates how many standard deviation it is from the mean in that case it is 2 (2.1) standard deviation. since it's negative it means it's below the mean so bottom 2.5%
I dont really get that :/ I get that its 2 Standard Deviation from the mean and thats its a negative so its in the bottom of the class but then how did you just get to 2.5%?
Does that mean if the z score is -5.1 then its in the bottom 5% of the class? And if the z score is -16.3 or something then its in the bottom 16% of the class?
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z score indicates how many standard deviation it is from the mean in that case it is 2 (2.1) standard deviation. since it's negative it means it's below the mean so bottom 2.5%
I dont really get that :/ I get that its 2 Standard Deviation from the mean and thats its a negative so its in the bottom of the class but then how did you just get to 2.5%?
Does that mean if the z score is -5.1 then its in the bottom 5% of the class? And if the z score is -16.3 or something then its in the bottom 16% of the class?
No, for further maths theres only 3 SD, 1SD= 68%, 2SD= 95%, 3SD= 99.7%
it doesnt stretch beyond 4 in this math :P
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No, for further maths theres only 3 SD, 1SD= 68%, 2SD= 95%, 3SD= 99.7%
it doesnt stretch beyond 4 in this math :P
Haha yeah I know the 68/95/99.7 rule but I dont know how he got from being 2SD to bottom 2.5% of the class. To me its like theres a massive step missing. . . .
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DONT WORRY I GOT IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! YAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYA!
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-1.7 x 2.85 + 55 = 50.155 ?
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DONT WORRY I GOT IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! YAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYAYA!
;)