Question

be accurate please and thanks.

Suppose that 30% of all students who have to buy a text for a particular course want a new copy (the 25 purchaser whereas the other of the book found your da (a) what are the mean value and standard deviation of the number who wants mean students standard deviation students t a ) (b) What is the probability that the number who want new copies is more than two standard deviations away from the mean value Round you to the The bookstore has 15 new coples and 15 used copies in stock. If 25 people come in one by one to purchase this text, what is the bay that they they want from current stock? Cinti Let the number who want a new copy. For what values of X will l 25 get what they want (Round you are to the

Answer 1

a)

mean of distribution=μ=np=

7.50

standard deviation σ=√(np(1-p))=

2.29

b)

2 standard deviation from mean values are μ -/+ 2*σ=(2.92,12.08)

probability =

1-P(3<=X<=12)=

1-∑x=x1x2     (nCx)px(1−p)(n-x)    =

1-0.9736=0.026

c)

probability =

P(10<=X<=15)=

∑x=x1x2     (nCx)px(1−p)(n-x)    =

0.189

d)

expected value =140*7.5+60*17.5 =2100

E(aX+b) =aE(X)+b