Kindly, indeed.

Thank you. I believe I've got it down now.

Prior:1/101

Test: Correct positive 95%

False positive 20%

1 of the 101 has the disease, with 95% probability of receiving a positive reading, denoting 1 x .95 = .95

And 100 don't have the disease, each with a 20% probability of a positive reading, denoting 100 x .2=20

.95 + 20 = 20.95

.95 / 20.95 = .045, denoting a 4.5% chance that someone receiving a positive reading has the disease.

Thank you again :)