Anonymous

# I HAVE NO IDEA WHAT THESE PROBABILITY QUESTIONS MEAN?

1) Suppose we have a diagnostic test for lung cancer that is 99% accurate both on those who have cancer and those who don't. .2 percent of the population have lung cancer, and we want to figure out the probability that a tested person has lung cancer given that the test result indicates that he or she has lung cancer.

This is like the drug case in the text. We will use the long form of Bayes' Theorem.

First, let L = has lung cancer, + = has tested positive for lung cancer. Notice that Prob(L) = .002.

Now what is Prob(+ | not L)?

Your answer should be a percentage (no decimals), e.g. 23% not 23.1%

2) Suppose we have a diagnostic test for lung cancer that is 99% accurate both on those who have cancer and those who don't. .2 percent of the population have lung cancer, and we want to figure out the probability that a tested person has lung cancer given that the test result indicates that he or she has lung cancer.

This is like the drug case in the text. We will use the long form of Bayes' Theorem.

First, let L = has lung cancer, + = has tested positive for lung cancer. Notice that Prob(L) = .002.

Now what is Prob(not L)?

Your answer should be a percentage (with one decimal point), e.g. 23.1%

3) Suppose we have a diagnostic test for lung cancer that is 99% accurate both on those who have cancer and those who don't. If .2 percent of the population have lung cancer, what is the probability that a tested person has lung cancer given that the test result indicates that he or she has lung cancer?

This is like the drug case in the text. Use the long form of Bayes' Theorem. Your answer should be a percentage (no decimals), e.g. 23% not 23.1%

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