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# S2 approximation help watch

1. what kind of approximation would you use for these:

1. A fair die is rolled and the number of sixes obtained is recorded. Using suitablle approximations find the probablility of:
a. No more than 10 sixes in 48 rolls of the die.

For a. the n is quite small, even though the p is small too so I always get confused whether to use binomial-poisson or not and since this question is in the normal approximations section of the book I dont know what to use because p isnt close to 0.5 either.
2. (Original post by fpmaniac)
what kind of approximation would you use for these:

1. A fair die is rolled and the number of sixes obtained is recorded. Using suitablle approximations find the probablility of:
a. No more than 10 sixes in 48 rolls of the die.

For a. the n is quite small, even though the p is small too so I always get confused whether to use binomial-poisson or not and since this question is in the normal approximations section of the book I dont know what to use because p isnt close to 0.5 either.
Personally I ignore those arbitrary conditions (although it is important to remember then and be able to recite them), and test out the poisson approximation like so: the tables (for Edexcel, at least) only go up to 10, so if the proposed lamba (i.e lambda = np) was greater than 10, then a normal approximation is suitable. If not, go for possion. (Basically, if you can use thet ables with poisson, go for it, if you can't then use normal).
3. (Original post by SeanFM)
Personally I ignore those arbitrary conditions (although it is important to remember then and be able to recite them), and test out the poisson approximation like so: the tables (for Edexcel, at least) only go up to 10, so if the proposed lamba (i.e lambda = np) was greater than 10, then a normal approximation is suitable. If not, go for possion. (Basically, if you can use thet ables with poisson, go for it, if you can't then use normal).
Thanks!

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