An experimenter is studying the effects of temperature, pressure, and type of catalyst on yield from a certain chemical reaction. She considers 6 different temperatures, 5 different pressures, and 4 different catalysts are under consideration.

a. If any particular experimental run involves the use of a single temperature, pressure, and catalyst, how many experimental runs are possible?
b. How many experimental runs are there that involve use of the lowest temperature and two lowest pressures?
c. Suppose that five different experimental runs are to be made on the first day of experimentation. If the five are randomly selected from among all the possibilities, so that any group of five has the same probability of selection, what is the probability that a different catalyst is used on each run?

a. For the experiment, there are 6 different temperatures (T), 5 different pressures (P), and 4 different catalysts (C). We can find the total number of combinations using the product rule.

N = T × P × C

N = 6 × 5 × 4 = 120

b) If we use only the lowest temperature, we have T = 1, and if we use the two lowest pressures, we have P = 2. We can find the total number of combinations using the product rule.

N = T × P × C

N = 1 × 2 × 4 = 8

c) If we perform 5 experimental runs with 4 possible catalysts, it is not possible to use a different catalyst each time. At least, 1 catalyst must be repeated twice. Then, the event "a different catalyst is used on each run" has a probability of 0.