Accuracy of Averages.

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Accuracy of Averages

Assignment Sheet Read Chapter 23 Assignment # 15 (Due Wednesday May 4th) Chapter 23 Exercise Set A: 1-5, 9 Exercise Set B: 1, 2, 6, 7 Exercise Set C: 1-6 Review Exercises: 1- 12 Special Review Exercises in the chapter would be good problems for early personal review for the final exam. They are not due, but good practice…

Overview Equation associated with average Use of Normal Curve Confidence intervals for averages Review of SE equations thus far…

Equations When drawing at random from a box: EV for average of draws = average of box SE for average of draws = SE for Sum/number of draws

Application of Normal Curve When drawing at random for a box the probability histogram for the average of the draws will follow the normal curve even if the contents of the box do not However, the number of draws must be large (30+) and you have to standardize the probability histogram

Predicting the Box from the Draws With a simple random sample The SD of the sample can be used to estimate the SD of the box The estimate is good when the sample is large. We can use the same method to get a confidence interval as we did in Ch 21.

Standard Error (SE) Standard error The standard error of the sample measures the likely amount that the sample statistic is off from the population parameter. It is a give-or-take number. Equations: SE for the Sum = SE for the average = SE for count = SE for percent =