1. Which of the following is true about probability density functions?
A. The total area under the density function below the x-axis is 2.0.
B. P (a) x P (b) is the area under the density function between two numbers a and b.
C. It calculates the probability of a random variable lying within a certain interval.
D. A graph of the density function must lie at or below the x-axis.
2. Which of the following distributions is appropriate when the probability of zero is very low, but the most likely value is just greater than zero?
A. triangular distribution
B. lognormal distribution
C. exponential distribution
D. beta distribution