Introduction to Quantitative Methods II Chapter 9

you looked at the incidence of depression in the classes of 2019 and 2020. The frequency table is given below.

	2019	2020	Total
Frequent Depression	37	47	84
Once per Month	31	22	53
Infrequent Depression	66	43	109
Total	134	112	246

With such a small sample, any relative frequency probabilities we might estimate would be subject to a large amount of estimation error. Let us assume that our sample size is much much larger (say 246,000) and we can reasonably calculate probabilities from this table.

1. What is the probability that a randomly selected student experiences frequent depression?
2. What is the probability of randomly selection a student who is in the class of 2019 and experiences frequent depression?
3. What is the probability of randomly selecting a student who is in the class of 2019 or experiences frequent depression?
4. Among the students of the class of 2019, what is the chance that a student experiences frequent depression?
5. Among those students who experience frequent depression, what is the probability that the student is in the class of 2019?
6. Are the events being in the class of 2019 and experiencing frequent depression independent? Justify your answer using probability.