Question 1068243: Steele Electronics Inc. sells expensive brands of stereo equipment in several shopping malls. The marketing research department of Steele reports that 33% of the customers entering the store that indicate they are browsing will, in the end, make a purchase. Let the last 24 customers who enter the store be a sample.
What is the probability 13 or more make a purchase? (Round the final answer to 4 decimal places.)
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! Can use the normal approximation to the binomial and compare with the exact number using the binomial distribution.
np=7.92 (mean)
np(1-p)=variance=5.3064; sd is sqrt (V)=2.304
Greater than 13 (or the same, which for a continuous function is essentially the same) is (13-7.92)/2.304=5.08/2.304=2.205
P z>2.205 is 0.0137.
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Can check with binomial
24C13(.33)^13*(.67^11)=0.0168
24C14(.33)^14(.67^10)=0.0065
24C15(.33)^15(.67^9)=0.002
Those 3 will be the major probabilities, and the exact binomial probability is 0.0235.
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