In an article, authors survey Black Friday shoppers. One question was "How many hours do you usually spend shopping on Black Friday?"
1. How many Black Friday shoppers should be included in a sample designed to estimate the average number of hours spent shopping on Black Friday if you want the estimate to deviate no more than 0.5 hour from the true mean?
2. Devise a sampling plan for collecting the data that will likely result in a representative sample.
Sampling theory says a correctly taken sample of an appropriate size will yield results that can be applied to the population as a whole. There is a lot in this statement but the two fundamental questions to ensure generalization are:
How is a sample taken correctly?
How big should the sample be?
A population is the group that you want to study for your investigation, and about which you will make a conclusion. Because you cannot always interview or survey an entire population because it is too large, or because you cannot reach all members to try out a new medicine, etc., you pick a sample , a smaller representative group, from which you will make generalizations about the population. For example, you and four of your classmates can be a sample of your class, a sample of your high school's students, a sample of your country and so on. You can define a sample as a more concrete portion of a population or populations that you choose to represent. A sampling frame is the largest sample that can be obtained from a population.
Apr 30th, 2015
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