Question

According to a Wired magazine article, of e-mails that are received are tracked using software that can tell the e-mail sender when, where, and on what type of device the e-mail was opened (Wired magazine website). Suppose we randomly select received e-mails.

Answer 1

a.The expected number of emails is 12

b. The variance and the standard deviation is 7.200 and 2.683

Calculation of expected number of emails, variance and standard deviation:

Given that

P = 0.40 and n = 30

a)

The expected value of received e-mails is

= n × p

= 30 × 0.4

= 12  

b)

The variance of emails received is

= n × p × (1 - p)

= 30 × 0.4 × 0.6

= 7.200

Now

The standard deviation of emails received is

= sqrt(variance)

= 2.683

We simply applied the above formula

Learn more about variance here:  https://brainly.com/question/24138432