Question

The DSM-IV (the major diagnostic manual for psychological disorders) notes that the prevalence of major depression is approximately 5.4% for the young and 1.5% for the elderly. The Beck Depression Inventory has a sensitivity of 87% and a specificity of 79%. What is the probability that an old person is depressed, given that they scored above the cut-off point on the Beck Depression Inventory? how much better the Beck Depression Inventory is at diagnosing young people than old people. What is that ratio?

Answer 1

a)Let A->Depression

B->Test Positive

P(A)=0.015

P(B|A)=0.87

P(B'|A')=0.79

b)For young people

P(A)=0.054

Hence, the inventory diagonises the young people well. Ratio=0.1913/0.0593=3.22