Question

The false positive rate for polygraph tests is thought to be unacceptably high. You have been offered a job by a firm who wants you to take a polygraph test. You are aware of the flaws inherent in polygraph testing and don't want to do it. Answer the following questions with regard to a polygraph test, which could be considered a diagnostic test for lying.

a) What are the null and alternative hypotheses for this situation?

b) What is the Type I error in this situation, and what is the consequence of making a Type I error?

c) What is the Type II error in this situation, and what is the consequence of making a Type II error?

d) You must evaluate the seriousness of the two types of error. Explain which type you think is more serious and why.

Answer 1

(a)

H0: Null Hypothesis: False positive rate for poygraph tests is low

HA: Alternative Hypothesis: False positive rate for polygraph tests is high (Claim)

(b) Type I Error: Rejection of a true null hypothesis

Suppose in reality False positive rate for polygraph is low. But, due to hypothesis testing we wrongly conclude that it is high. Type I eoor is committed in this case. The consequence of this error is that we will be carrying out necessary remedial actions, which are not at all required.

(c) Tye II Error: Failing to reject a false null hypothesis

Suppose in reality: false positive rate for polygraph is high. But, due to hypothesis testing, we wrongly conclude that it is low. Type II Error is committed in this case. The consequence of this error is that we will not be carrying out any necessary remedial actions, thinking that everything is going on nicely, whereas situation warrants that action should be taken.

(d) Type II Error is more serious because the consequence of Type I error is just that we be doing corrective actions, not required at all. But, in the case of Type II Error we will not do anything, which will lead us in trouble subsequently.