Edexcel S2 - 27th June 2016 AM

How many marks was the P(7<R<10) question

Does anyone know if @kprime2 is DOIN model answers


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Well, S2 is sort of unpredictable. That mark would easily get you a solid A with 84+ UMS on IAL June 14 or June 15, but would be a high B on UK 15 or IAL Jan 16... I say relax until the grade boundaries are released - even then, you could still be severely underestimating yourself!

Well, S2 is sort of unpredictable. That mark would easily get you a solid A with 84+ UMS on IAL June 14 or June 15, but would be a high B on UK 15 or IAL Jan 16... I say relax until the grade boundaries are released - even then, you could still be severely underestimating yourself!

What was the answer to this question????!

0.5

I just did the area so (10-7)*probability. I can't rightly remember what the probability was, maybe 1/4? If so it would just be 3/4.

THIS IS THE QUESTION FOR THE normal APPROX.

X-B(N,0.2) USING NORMAL APPROX AND GIVEN THAT P(X>55)=0.0401
FIND N

AND ANSWER:
X-B[N,0.2]= W-N[X,Y"] X IS MEAN Y" IS VARIANCE " MEANS SQUARED

P(X>55)=P[W>55.5)=P(Z>([55.5-X]/Y)=0.0401

P(Z<([55.5-X]/Y)=1-0.0401=0.9599

USING TABLE

(55.5-X)/Y=1.75
55.5-X=1.75Y
1.75Y+X=55.5 NOW USING THE BINOMIAL PARAMETERS
WE CAN FIND Y AND X IN TERMS OF N
X=0.2N
Y"=0.2*0.8N Y"=0.16N Y=0.4N! WHERE !=SQUARE ROOT
SO 1.75(0.4N!)+0.2N =55.5
0.7N!+0.2N=55.5
0.2N+0.7N!-55.5=0 NOW SOLVE THIS USING QUADRATIC FORMULA
YOU GET N!=15 OR (-18.5)
SO N = 225 OR 342.25 BUT WE ARE DEALING STUDENTS
SO N=225 ONLY
don't KNOW WHY PEOPLE ARE GETTING 200

But the distribution was U~[5,9] so would it not be 2 x 0.25??

Could someone link me the unofficial scheme?

Sure. How did you find the paper?

I think its pretty easy. I just spent 45 minutes to finish the paper.

The only thing I'm not sure about is the question concerning car test, i dun know if its talking about 20 cars or 54 cars.