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# S2 - Suitable model of distribution? watch

1. Sue throws a fair coin 15 times and records the number of times it shows heads. State the distribution to model the number of times the coin shows a head.

as n=15 and p=0.5 i said normal, but the mark scheme says binomial.
surely a coin toss has a normal distribution? or is the answer to these types of question always binomial distribution?
2. (Original post by jbuck100)
Sue throws a fair coin 15 times and records the number of times it shows heads. State the distribution to model the number of times the coin shows a head.

as n=15 and p=0.5 i said normal, but the mark scheme says binomial.
surely a coin toss has a normal distribution? or is the answer to these types of question always binomial distribution?
its binomial.
for coin flips its usually always binomial; as it has only 2 outcomes and fits the criteria better.
3. It's a discrete random variable with a uniform rate of occurance, so ofcourse it's binomial - normal is for continous variables.
4. cool, although isnt poisson also a discrete random variable with a uniform rate of occurance?
i assume the answer would never be poisson though unless they ask like 'what would be a suitable approximation to use'..
5. (Original post by jbuck100)
cool, although isnt poisson also a discrete random variable with a uniform rate of occurance?
i assume the answer would never be poisson though unless they ask like 'what would be a suitable approximation to use'..
It cannot be poisson as it has to satisfy that n is large and p is small
6. (Original post by jbuck100)
cool, although isnt poisson also a discrete random variable with a uniform rate of occurance?
i assume the answer would never be poisson though unless they ask like 'what would be a suitable approximation to use'..
It can't be poisson as the variance and mean will be far away from eachother.
7. awesome

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