Suppose the prevalence of a disease is 2 per thousand people. A screening test has a specificity of 95% and a sensitivity of 99%. Describe each of the probabilities.
i. Describe each of the implied probabilities
ii. What proportion of those tested will be positive?
iii. Among those tested positive, what proportion actually have the disease?
iv. How would the numbers in ii and iii change if the prevalence were even smaller?