CHAPTER 14Sample Size Determination

Photo illustration of a U.S. city during the night.

Given all the changes in the world and the associated changes in the marketing research environment, one might expect substantial changes in the process of sample size determination. The fact is there are no changes in the area of sample size determination.

It is absolutely critical to keep in mind that all of the calculations discussed in this chapter assume that we are working with a random sample as defined in the previous chapter. Frequently, we see sample size and/or sampling error calculations done for samples that are clearly not random samples. This is totally inappropriate and, really, deceptive. The fact is that if we have a sample that does not meet the requirements of random sample, then the level of sampling error cannot be calculated and any calculations related to sampling error or sample size are totally inappropriate.

It does not matter how big the sample is even if it is in the hundreds of thousands or millions; if it is not a random sample, then these calculations are not valid. There are bases to estimate sampling error for other types of probability ...

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