OCR MEI - S1 - 20th May 2015

Original post by Qwertykeyboard15

I think the last question said about him picking out more than 2 of the ones he doesn't like before he has a chocolate he does like.
This means that he could have had 2 cherries, 3 cherries etc up to all 6 cherries before eating one that he likes.
So you start with 6/20 x 5/19 x 14/18 (that's the probability of now picking one he likes) and then you do it again but with 3 cherries, then 4, 5, and 6

No becauseI believe the q said "prob. of him having to eat more than 2 before finds one he likes". it may be that he picks all 6 cherry ones before he finds one he doesn't like, we don't know. It just asks you to find the probability of him not getting one he likes from the first 2 (i.e. 2 cherries).

Reply 424

Original post by lilmi5s_elmo

No becauseI believe the q said "prob. of him having to eat more than 2 before finds one he likes". it may be that he picks all 6 cherry ones before he finds one he doesn't like, we don't know. It just asks you to find the probability of him not getting one he likes from the first 2 (i.e. 2 cherries).

Yes you're correct, nice to see someone here understands.

Reply 425

Tee546

If I rounded the last answer to 0.079 which is roughly equivalent to 3/38 will I pick up full marks on that Q?

Reply 426

Original post by Tee546

If I rounded the last answer to 0.079 which is roughly equivalent to 3/38 will I pick up full marks on that Q?

You'd be very unlucky to lose a mark, but don't discount it as I'm sure you know S1 mark schemes are by far the most stupid. You should be completely fine, it's 3.d.p and entirely correct so unless the exam was found ridiculously easy and they need to invent new ways to make us lose marks, you'll be absolutely fine!

Reply 427

Tee546

Original post by joe12345marc

You'd be very unlucky to lose a mark, but don't discount it as I'm sure you know S1 mark schemes are by far the most stupid. You should be completely fine, it's 3.d.p and entirely correct so unless the exam was found ridiculously easy and they need to invent new ways to make us lose marks, you'll be absolutely fine!

Nice one, cheers! I had an absolute nightmare with the easiest question on the paper: the on with the deck of cards and aces. I did 1- P(ace then ace), will I get a follow through mark using that answer for my expectation?

Reply 428

bethygirl

3

Original post by yoomi

Hey

I am just wondering how did u do the hypothesis test question !
The thing that confused me, that there wasn't p=0.78 in the table :frown:

so could not finish my answer

Thank you

The key was to do an individual binomial distribution for both 19 and 20 and add them together which was part of the working out for the previous question. This came to 0.046 which is 4.6% which means not sufficient evidence to reject null hypothesis, then the next question asked what if it was done at 5% significance level which would be it was sufficient evidence to reject null hypothesis because 4.6 is less than 5 :smile:

I'm not sure if this was the correct way to do it but I came out with the right answer.

Reply 429

Original post by Tee546

Nice one, cheers! I had an absolute nightmare with the easiest question on the paper: the on with the deck of cards and aces. I did 1- P(ace then ace), will I get a follow through mark using that answer for my expectation?

I'm sorry I do not remember the question, any context please? :smile:

Sorry

Edit: You usually do get 1 FT mark for expectation, BUT NOT ALWAYS so not sure :/

Reply 430

Tee546

Original post by joe12345marc

I'm sorry I do not remember the question, any context please? :smile:

Sorry

Edit: You usually do get 1 FT mark for expectation, BUT NOT ALWAYS so not sure :/

When you had to work out the probability of neither card being an ace?

Reply 431

Original post by Tee546

When you had to work out the probability of neither card being an ace?

You'd almost certainly get a follow through mark for working out expectation as long as you did it with your own answer

Reply 432

princessliz

Is there an unofficial mark scheme for this paper anywhere?

Reply 433

Duskstar

13

Original post by princessliz

Is there an unofficial mark scheme for this paper anywhere?

Page 11 iirc

Reply 434

princessliz

Original post by thecalmmorning

I had no idea how to do that :frown:

I've no idea howitzer guessed it but I just did 1-(5/6)^3 on my calculator and got 91/216.... It was a miracle

Reply 435

princessliz