In: Statistics and Probability
If np greater than or equals 5 and nq greater than or equals 5, estimate Upper P left parenthesis at least 8 right parenthesis with n equals 13 and p equals 0.6 by using the normal distribution as an approximation to the binomial distribution; if np less than 5 or nq less than 5, then state that the normal approximation is not suitable. P(at least 8) =?
Let X be the number of successes in n trials. X has a Binomial distribution with parameters, number of trials n=13 and the success probability, p=0.6
Now the test for np and nq
ans: np greater than or equals 5 and nq greater than or equals 5 and hence we can use normal approximation to binomial distribution.
First we get the following
The expected value of X is (using the formula for the Binomial expectation)
The standard deviation of X is (using the formula for the Binomial distribution)
We can say that X has approximately a normal distribution with mean and standard deviation
The probability that X is at least 8 (which is 8 or more) is
ans: P(at least 8) = 0.5675 (using the normal approximation)