Question

Suppose that 30% of all students who have to buy a text for a particular course want a new copy (the successes!), whereas the other 70% want a used copy. Consider randomly selecting 25 purchasers. (a) What are the mean value and standard deviation of the number who want a new copy of the book? (Round your standard deviation to two decimal places.) mean

Answer 1

Answer: The mean and standard deviation are 7.5 and 2.29 respectively.

Explanation:

Since we have given that

Percentage of all students who have to buy a text for a particular course want a new copy = 30%

n = 25

p = 0.3

So, the mean value of the number who want a new copy of the book is given by

`\bar{x}=np=25* 0.3=7.5`

and the standard deviation of the number who want a new copy of the book is given by

`\sigma=√(npq)=√(25* 0.3* 0.7)=√(5.25)=2.29`

Hence, the mean and standard deviation are 7.5 and 2.29 respectively.