Question

Coliform bacteria are distributed in a river at an average concentration of 1 per 20 cc of water. If we draw from the river a test tube containing 10cc of water, what is the probability that the sample contains exactly 2 coliform bacteria

Answer 1

Answer:

0.5

Step-by-step explanation:

Given that: An average concentration of 1 coliform bacteria per 20 cc of the river water.

This implies that in 20 cc of the water, it is certain that 1 coliform bacteria would be found. So that:

pr(1 bacteria in 20 cc of water) = 1

i.e the probability of getting 1 bacteria in 20 cc of water is 1.

The probability of the 10 cc sample of water containing 2 coliform bacteria can be determined as:

pr(2 bacteria in 10 cc of water) = $\frac{1}{2}$

                                                   = 0.5