# Probability Questions on Immunity and IQ

2. The probability that a person is immune to a certain disease is 0.40.

a) What is the probability that 4 people will have the disease in a sample of 12 people

b) Find the mean number of people who have immunity in a sample size of 12.

c) Find the standard deviation for the same sample

3. If the capacities of the cranial cavities of a certain population are approximately normally distributed with a mean of 1400cc and a standard deviation of 125, find the probability that a randomly selected person from the given population will have a cranial capacity greater than 1450cc.

4. IQ scores are normally distributed with a mean of 100 and a standard deviation of 15. In a random sample of 50, approximately how many people will have IQ scores between 95 and 105

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#### Solution Preview

2) p = .40

a) P(4)= (12 C 4) *( .4^8) * (.8^4)( Prob that 8 people dont have it and 4 people have it and Prob of not having = .4)

= .1328

b) Mean Number = N*p = 12*.4 = ...

#### Solution Summary

3 probability questions are answered, including finding standard deviations and means with all calculations displayed