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How Do I Determine Adequate Sample Size?

The sample size starts the planning of any statistical study. The size must be big enough that it can make an effect and become scientifically significant, but the sample size cannot become too big. If the size is too big, it will affect nothing and become invalid, according to the Department of Statistics of the University of Iowa website. To figure out an adequate sample size, which is equal to or greater than 80 percent, confidence is needed.

Instructions

- 1
  Figure out your confidence level. The level reveals how confident you are in the polls. It represents how often the true percentage of the population will pick an answer. Most researchers choose between a 95 and 99 percent confidence level.
- 2
  Figure out the confidence interval of the sample size. The interval is a plus or minus system that assures your samples. For example, if you have an interval of 6 and 48 of your samples are picked, your confidence interval equals 48+6 and 48-6, or 54 and 42.
- 3
  Calculate the population of the ranged poll. This number is the number of people who took the poll. If you do not know the exact number, estimate.
- 4
  Plug in the numbers into a sample size calculator to reveal your sample size. Several are freely available on the Web.

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