1. Suppose that an event A contains 10 observations and event B contains 15 observations. If intersection of events A and B contains exactly three observations, how many observations are in union of these two events?
A. 0 B. 10 C. 22 D. 28
2. Approximately how much of total area under the normal curve will be in interval spanning two standard deviations on either side of the mean?
A. 50% B. 68.3% C. 95.5% D. 99.7%