The probability of a randomly selected adult in one country being infected with a certain virus is 0.004. In tests for the virus, blood samples from 15 people are combined. What is the probability that the combined sample tests positive for the virus? Is it unlikely for such a combined sample to test positive? Note that the combined sample tests positive if at least one person has the virus.

This problem involves students who have taken Calculus in high school. Assume that 35 percent of students have taken calculus in high school. Of those who have taken calculus in high school, 75 percent plan to major in science. Of those who did not take calculus in high school, only 20 percent plan to major in science. What is the probability that a randomly selected student plans to major in science?

The local weather forecaster predicts that there is a 12% chance of rain on each day next week. Assuming his prediction is accurate and that the chance of rain in a given day does not depend on the chance of rain in a different day, what is the probability it will rain on at least 4 of the days next week?

It has been determined that there is a 75% chance of a person using their seatbelt when sitting in the back seat of a car. If 8 people leave a party and take cabs home, which of the following would be used to find the probability that 6 of them use their seatbelt when sitting in the back seat?