You want to describe the number of consumers in a fixed population who prefer Brand X. You are dealing with a total population of 40 consumers, of which 30 prefer Brand X and 10 prefer Brand Y. You survey 20 of those consumers.
The first step in selecting a probability distribution is matching the data with a distribution’s conditions. Checking the hypergeometric distribution:
The conditions in this example match those of the hypergeometric distribution.
If you have a probability from a different-sized sample instead of a success rate, you can estimate initial success by multiplying the population size by the probability of success. In this example, the probability of success is 75% (.75 x 40 = 30 and 30/40 = .75). |
The three parameters of this distribution are initial Success, number of Trials, and Population size. The conditions outlined in this example contain the values for these parameters: a population Size of 40, sample size (Trials) of 20, and initial Success of 30 (30 of 40 consumers will prefer Brand X). You would enter these values as the parameters of the hypergeometric distribution in Crystal Ball.
The distribution illustrated in Figure 102, Hypergeometric distribution shows the probability that x number of consumers prefer Brand X.
