Please someone explain this to me. I have done this problem twice (with different values). I have no problem with the math part but I absolutely can’t understand the reasoning at the end.

These are the numbers and results from the second time I worked the problem. I got everything right up 'til the last part both times.

99 polygraph tests.

22 have wrong results.

77 have correct results.

.01 significance level.

Test the claim that such polygraph tests are correct less than 80% of the time.

Based on the results, should polygraph tests be prohibited as evidence in trials?

A) Identify the null and alternative hypotheses: Null: p=.8, ALT: p<.8 - correct.

B) Identify the test statistic: -.55 correct

C) Identify the p-value: .2912 correct

D) Identify the conclusion about the null hypothesis and the final conclusion that addresses the claim.

Fail to reject the null hypotheses - correct

There is not significant evidence to support the claim that polygraph tests are correct less than 80% of the time - correct.

This is where I have issues -

Based on the sample proportion of correct results, polygraph tests (do not) appear to have a high degree of reliability that would justify the use of a polygraph in court, so polygraph results should be (prohibited) as evidence in trials.

The parts in the parentheses are the correct answers and are the parts I can’t seem to get right. I failed to reject the null hypothesis so I don’t know whether or not they have less than an 80% correct rate. Is 80% considered bad? How the hell am I supposed to know? Is this some common knowledge? If I had rejected the null hypothesis, that would mean that they are correct less than 80% of the time - yes? But, I didn’t so how am I supposed to put 2 and 2 together to determine that they shouldn’t be allowed in court?