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# MEI S2 easier than S1??? your views watch

1. (Original post by Willa)
yea todays s2 was a ***** - it's cos they werent expressley saying which distribution to you, and so i couldnt think of the parameters i need to use in any of them - GRRRR
i went through the whole paper without using the normal distribution, and this didnt occur to me until I neared the end of the exam! Like yourself, I couldnt find the values I needed for any of them (i.e. z or the standard deviation or the variance)
2. (Original post by Willa)
yea that question which said "Use the possion distribution to find the expected frequencies correspondign to the given frequencies" - i was like "WTF!?".

I hope that what it was asking you to do is use the possion distribution to predict the frequencies, and then compare those to the actual frequencies and see if it's a good fit!

What did others do?
i read this question aboutr 16 times, and still didnt understand it. There were others in my year who felt the same so I knew it wasnt just me being thick! The last part of that question, when it changed to a 60 hour interval was really badly worded too!
3. (Original post by Katie Heskins)
yeh I did that....and found it was a good fit....did u get that??
did you get the last bit...show something or antoher = 66p?
i found that two of them fit well, but the other two were only a good fit to just one sig fig, and not the three sig fig in the question so I wrote it was good for some values but not the best model as the results from Poisson were not that close to the actual values. I know its a vague answer and will probably get zero since im answering both yes and no at the same time, but they were the figures i got!
4. (Original post by physicsboy)
i read this question aboutr 16 times, and still didnt understand it. There were others in my year who felt the same so I knew it wasnt just me being thick! The last part of that question, when it changed to a 60 hour interval was really badly worded too!
Well actually I didn't get it at first, so left it until i'd been through all paper, and then I realised that there were very similar excercises that we had doen in the S2 text book, where you just use the Poisson Distribution, stick your x value in for whatever you wanted e.g p(X=0) = e^-0.5, where 0.5 was lambda, and so on until you get p(X>3) (ie. P(X> or = to 4)).
The with your probabilities multiply it by 40 to get your expected frequencies, does anyone remember working through it in the Poisson chapter of the text book???

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