Qualification > University

Maths & Physics Help

<< < (6/9) > >>

omarsubei:
Hi my exam's in 12 hours, and I just don't get statistics. Please help with this question,

Consider the 10 data items x1, x2, ... x10. Given that Sum(xi)  = 1341 and the standard deviation is 6.9, find the value of the mean .

The answer is:

6.92 = 1341/10 - mean2

and then the answer works out to be +/- 9.3 .

I get the method, I just don't get why they divided by 10 ?

astarmathsandphysics:
There must be more to the question than that. Cabn you post the question?

omarsubei:
I'm sure that's the whole question. I don't know what you mean by post it

astarmathsandphysics:
This is an old topic . Can you you ropost to make it current?

astarmathsandphysics:

--- Quote from: roma on May 06, 2009, 06:39:58 pm ---Hey, i needed some help on this question.

Prove p = 0.08512 B = 0.01881 A = 0.03119 simultaneously,
20 =1/(A + B)
23 =1/(A + Be^-5p)
25.5 =1/(A + Be^-10p)

--- End quote ---

1)20 =1/(A + B)
2)23 =1/(A + Be^-5p)
3)25.5 =1/(A + Be^-10p)


Turn everything upside down

1/20 =(A + B)
1/23 =(A + Be^-5p)
1/25.5 =(A + Be^-10p)
top take away next onw gives B-Be^-5p=3/460 (4) and top take the third gives 5.5/510=B-Be^-10p Divide these 2 equtions by each other to give

(1-e^-5p)/(1-e^-10p)=0.604

sub x=e^-5p to give(1-x)/(1-x2)=0.604

so 1-x=0.604-0.604x2
so0.604x2-0.604x+0.396=0 Solve this and sub into 4 to find B then into 1 to find A

Navigation

[0] Message Index

[#] Next page

[*] Previous page