1. Accuracy of Averages

2. 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…

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

4. 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

5. 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

6. 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.

7. 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 =