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. Author manuscript; available in PMC: 2015 Jul 28.
Published in final edited form as: Neoreviews. 2014 Apr 1;15(4):e133–e150. doi: 10.1542/neo.15-4-e133

Figure 7.

Figure 7

Confidence interval. The true population mean (birthweight in this example) is shown by the black circle. The white circle represents the mean of a small sample (eg, your hospital deliveries). The 95% confidence interval is shown by the solid line (and is mean ± 1.96 × SEM). Increasing confidence from 95% to 99% will widen the range of the confidence interval to mean ± 2.58 × SEM). Increasing the sample size (eg, including all births in a county or state) will narrow the confidence interval.