Consider a joint PMF for the results of a study that comparedthe number of micro-strokes a patient suffered in a year (F) and anindex (S) that characterizes the stress the person is exposed to.This PMF represents the probability of a randomly picked personfrom the studied population having F=f micro-strokes and S=s stressindex.
| f=0 | f=1 | f=2 | f=3 |
| s=1 | 0.1 | 0.04 | 0.04 | 0.02 |
| s=2 | 0.25 | 0.1 | 0.12 | 0.03 |
| s=3 | 0.15 | 0.06 | 0.03 | 0.06 |
a) The conditional PMF for the number of strokes F given stressindex S=3.?
b) The expected number of strokes and the variance of thismagnitude for patients with S=3??
c) The conditional PMF for strokes and stress index given eventA={(S,F) /s<3 and f<2}?
d) There were 3000 patients in the study. How many you expect tofind that have F and S in A (same A as above)??
e) What is the average stress index in this population? (hint:the marginal probability function above may be helpful)
