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# S2 edexcel chapter 5 question watch

1. Can someone tell me the breakoff point for how close to 0.5 the probability must be to approximate using normal distribution? I don't know if 0.4 or 0.3 are close enough etc
2. (Original post by Uzui21)
Can someone tell me the breakoff point for how close to 0.5 the probability must be to approximate using normal distribution? I don't know if 0.4 or 0.3 are close enough etc
There isn't one. Questions will normally tell you when to use an approximation.
3. (Original post by NotNotBatman)
There isn't one. Questions will normally tell you when to use an approximation.
There are questions that tend to ask you to choose the type of approximation, choosing whether or not to use poisson or normal (from binominal) has the difference that for normal p is close to 0.5 and poisson is small. But I'm unsure how close to 0.5 is the breakoff point.
4. (Original post by Uzui21)
There are questions that tend to ask you to choose the type of approximation, choosing whether or not to use poisson or normal (from binominal) has the difference that for normal p is close to 0.5 and poisson is small. But I'm unsure how close to 0.5 is the breakoff point.
There isn't a break off point; it's obvious which to use in the question, as n has to be large to approximate a binomial to a poisson distribution.

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