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NEED HELP SOLVING. If you can show me too how it is done on EXCEL specially on \

ID: 3245405 • Letter: N

Question

NEED HELP SOLVING. If you can show me too how it is done on EXCEL specially on "e". THANK YOU!

In a given hour, 30 individuals enter a certain store. Past experience indicates that 30% of all individuals entering the store decide to make a purchase. Based on the relevant binomial distribution, answer the following questions about X, the number of customers entering the store will make a purchase:

a)    What is the probability X is exactly 3? -----> My answer : .0072

b)    What is the probability that X is no more than 10? My answer------> .7304

c)     What is the probability that X is at least 15? -----> My answer ------> .0619

d)    Determine the mean and standard deviation of X. My answer ------> Mean = 9 and St. Dev. 2.51

e)    What is the probability that X will be within two standard deviations of the mean?

Explanation / Answer

a)

P(X=3) = 30C3 * 0.3^3 * 0.7^27 = 0.0072

b)

P(X<10) = BINOMDIST(10,30,0.3,TRUE) = 0.7304

e)

approximating normal distribution and using emperical rule

95% of data lies within 2 standard deviation

hence probability = 0.95