Question

Steele Electronics Inc. sells expensive brands of stereo equipment in several shopping malls. The marketing research department of Steele reports that 40% of the customers entering the store that indicate they are browsing will, in the end, make a purchase. Let the last 29 customers who enter the store be a sample.

a. How many of these customers would you expect to make a purchase? (Round the final answer to the nearest whole number.)

Number of Customers            

b. What is the probability that exactly six of these customers make a purchase? (Round the final answer to 4 decimal places.)

Probability            

c. What is the probability 18 or more make a purchase? (Round the final answer to 4 decimal places.)

Probability            

d. Does it seem likely at least one will make a purchase ("likely" refers if the probability is more than 70%)?

(Click to select)  No  Yes

Please help me to solve C part of it

Answer 1

a)

expected to make a purchase =29*0.4 =11.6

b)

here this is binomial with parameter n=29 and p=0.4

P(X=6)=

(29C6)p6(1−p)(29-6)    =

0.0154

c)

P(X>=18)=1-P(X<=17)=

1-∑x=017 (29Cx)px(q)(29-x) =

0.0135

(use ti-84 calculator 1-binomcdf(29,0.4,17) function to get above probability

d)

probability at least one will make purchase =1-P(no one purchase) =1-(1-0.4)²⁹ =1.0000

since above probability is higher than 70% ; therefore Yes