GMO Statistics Part 27. Testing for bad outcomes when you don't know the answer

This is the first of a series of posts about how to diagnose damage to the body.

The above panel shows as red dots  14 cases of breast cancer being present in 1000 representative adult women.

In this post we consider how this dreadful disease is detected and diagnosed.

It is customary to screen for breast cancer using X-ray imaging. This is known as a mammogram.

Let us suppose that all these 14 unfortunate cancer afflicted women were given mammograms, and the outcome is represented as a yellow filled in square to indicate positive indications of breast cancer from the mammogram. This is how the results would look:

The test shows 11 of the women with cancer had a positive mammogram  and 3 women were missed by the mammogram test. This absence of yellow background behind the red dots is called a false-negative result, because even though the mammogram test was negative, the poor women still had breast cancer.

This brings me to a question I have for any women reading this blog posting.

If you had a positive mammogram result given to you, and didn't know your breast cancer status, how would you react if you were told your test was positive? What would you believe to be the odds that you don't have breast cancer even though the test was positive? Would you be dreadfully depressed? Does the above panel help you in coming to a decision? Do you have a better way to examine this issue?


Continued....as

GMO Statistics Part 28. The full story matters for sound judgement about what a test result means 



h/t N. Silver