Question

1. Assume the random variable X represents the concentration of bacteria in a contaminated liquid, and that X is normally distributed with a mean µ=250 ppm and a standard deviation σ=70 ppm. Compute the approximate probability that Danielle would randomly select a container with a reading greater than 140 ppm.

Now, suppose that the value of the standard deviation was smaller, 40 ppm instead of 70 ppm. What would this tell us about the bacteria concentration in randomly selected container?

A. The graph would be more spread out.

B. There would be a higher probability of obtaining an extreme value.

C. The bacteria themselves would be smaller.

D. The various concentration values would be less variable.

Answer 1