Biology 2244A/B Lecture Notes - Lecture 7: Confidence Interval, Sampling Distribution, Mercury-Redstone 3
2 Jan 2017
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Recall: probability sample is a sample chosen by chance. The sampling distribution of x bar tells us how close to mu the sample mean x bar is likely to be. A confidence interval says how close to x bar the unknown population mean mu is likely to be. The 68-95-99. 7 rule for normal calculations says that in 95% of all samples, the sample mean x bar lies within two standard deviations of the population mean mu. In the example of the height of american boys, the interval of numbers between the values x bar 1. 4 and x bar + 1. 4 is called a 95% confidence interval for mu. Our confidence interval for the mean height of all 8-year-old boys is 132. 5 1. 4. Most confidence intervals take the form estimate margin of error. The estimate is the center of the interval; our unbiased guess for the value of the unknown parameter, based on the sample data.
