If the false positive rate is 5 percent, 50 out of every one thousand will test false positive. An additional person will test true positive. Therefore 51 will test positive. The probability a positive tester being positive is 1 out of 51. Multiply to 2 out of 102, and it becomes clear .02 overestimates the true value of those who would test positive as 2 hundredths is greater than 2 hundred-and-secondths.
If the false positive rate is 5 percent, 50 out of every one thousand will test false positive. An additional person will test true positive. Therefore 51 will test positive. The probability a positive tester being positive is 1 out of 51. Multiply to 2 out of 102, and it becomes clear .02 overestimates the true value of those who would test positive as 2 hundredths is greater than 2 hundred-and-secondths.