Opinion poll analysis
Imagine 700 people have been randomly chosen and asked about their preferences among the candidates A, B, and C. The candidate A gets 20% of the votes.
What can we deduce from the poll results, if the population size is 1.6 million, and we want to be 99% sure? We feed the tool with the input data n=700, m=140, N=1600000, and r=99%.
The output gives five cases. Let us consider the realistic case: there is 99% probability that candidate A has between 261744 and 386102 votes,
which is between 16.36% and 24.13% of the total population. Deviations from the expected value of 20% are -3.64% and +4.13%.
Prevalence of a disease
Around Y2K an outbreak of mad cow disease occurs. The authorities in many countries want to know what portion
of their animals is infected. Let us assume that in the population of 200000 animals they test a random sample
of 3000, and find zero positive cases. The input data are n=3000, m=0, and N=200000,
for confidence level we choose 95%. The authorities are interested in the pessimistic case of the results: the lowest
estimation with 95% probability. From the output table we get Mmin=0 and Mmax=198,
which means that not more than 198 animals are infected within the whole population.
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