I would like to double check my interpretation of a probability question.
2% of a population have a given medical condition. There is a medical test for that condition with 90% accuracy.
If a person tests positive, what is the probability the person actually has the condition?
Based on this, I have determined that the question is looking for P(D|pos)
Let pos = positive test result
Let D = condition of having the medical condition
- P(D) = 0.02
- P(pos|D) = 0.9
- P(pos|Dc) = 0.1
Question:
- Does my interpretation look correct?
- Have I found all the correct ingredients?
EDIT: Assuming that, with the term "90% Accuracy", we mean that Both Sensitivity and Specificity are 90%,
Yes, your interpretation is correct. Using your ingredients and Conditional probability's definition you get
$$\mathbb{P}[D|\text{pos}]=\frac{0.02\times0.90}{0.02\times0.90+0.98\times0.1}\approx15.52\%$$