Chapter 21, Problem 18E

(a)

To determine

To explain what is meant by the power of the test in this context.

Explanation of Solution

It is given in the question that spam filter try to sort your e-mails deciding which are real messages and which are unwanted. The filter reads each incoming e-mail and assigns points to the sender, the subject, key words in the message and so on. Thus, in this context, we can say that power of the test is the probability of correctly rejecting a false null hypothesis. And power of the test is the probability that the filter spots the spam.

(b)

To determine

To explain what could you do to increase the filter’s power.

Answer to Problem 18E

Bank should raise the cut-off power.

Explanation of Solution

It is given in the question that spam filter try to sort your e-mails deciding which are real messages and which are unwanted. The filter reads each incoming e-mail and assigns points to the sender, the subject, key words in the message and so on. Thus, to increase the filter’s power, we shouldlower the cut-off score because the probability of correctly filtered emails would be increased.

(c)

To determine

To explain what is the disadvantage of doing that.

Explanation of Solution

It is given in the question that spam filter try to sort your e-mails deciding which are real messages and which are unwanted. The filter reads each incoming e-mail and assigns points to the sender, the subject, key words in the message and so on. Thus, the disadvantage of doing that is that more real emails would end up in the spam mailbox.