Illuminating Statistical Analysis Using Scenarios and Simulations

8Amount of Evidence II

Statistical Scenario—Amount of Evidence II

What happens to our confidence interval as we increase our sample size?

What is a good sample size to use?

As I wrote at the end of Chapter 5, “the uncertainty due to sample size is incorporated into various statistical formulas.” Notice how the “trick” formula incorporates sample size.

Since is in the denominator, the confidence interval narrows as the sample size increases: When increases, the standard error decreases and so margin of error decreases. As the amount of evidence increases, uncertainty decreases and the confidence interval can narrow its focus.

Table 8.1 shows results when the margin of error ) is calculated for various sample sizes with equal to 0.5. Margin of error decreases as increases. ...