A laboratory blood test is 95% effective in detecting a certain disease when it is, in fact, present. In other words, the blood test has 95% sensitivity. However, the test also yields a "false positive" result for 1% of the healthy persons tested.(That is, if a healthy person is tested, then, with probability 0.01, the test result will imply that he or she has the disease).

If 0.5% of the population actually has the disease, what is the probability that a person has the disease given that the test result is positive? Write down in decimal number up to 4 digits (ex. 0.1234)