# Chapter 23

 Finding The SE of the Average  (of Box) SE for the average says how far the average of the dras is likely to be from the average of the box Formula = SE/#Draws Example: Draws = 25 Average of box with numbers (1,2,3,4,5,6,7) Ave box = 28(sum of Numbers)/7 = 4SD = 2EV = [(#draws) x (ave of box)] = 25 x 4 = 100SE = Square Root (#draws) x SD] = 5 x 2 =10 Box Averages EV of box = Averages = 4SE of box = SE for (Sum of Box)/(#draws) 10/25 = .4 So the Average/EV of the (box) is 4 with a Chance error of .4 Using the Normal Curve to estimate more Estimate that the average of the draws will be more than 4.2 #draws =100ave = 4EV = 4 x 100 = 400SD = 2SE = square root(100) x 2 (SD) = 20 SE of Box = 20/100 = .2 Ave= 4 give or take .2 convert into SU 4 (Average) - 4.2/ 2 (SE) = 1 (SU)   Solve for above 1 using normal scale = Area between 1 = 68% - 100% = 32% /2 = 16% SE with no givin SD Wants to know average incomes of 25000 families. 1000s families are sampled#draws = 1000total income= 62,396,714Ave income = 62,396,714/1000 =62,400SD = Unknown (SD is Found Using BootStrap Method [section, chp 21]) SD (BootStrap Method) = 53,000 SE can now be Caluclated SE for sum = square-root (#draws) x SDSE =  31.6 x 53000 = about 1,700,000 now we need the SE for the Average (62,400) SE for Ave = SE/#draws = 1,700,000/1000 =1700 Answer = 62,400 +- 1,700 Which SE SE shows the likely size of the amount off. It is a give-or-take number SE for sum = Square Root (#draws) x SD SE for Averages = SE for Sum/#draws SE for count = SE for Sum, From box (1,0)  SE for Percent = (SE for count/#draws) x 100. Sampling Average Estimates the population average but is off by a little. The little is the SE Authordamea134 ID306365 Card SetChapter 23 DescriptionThe Accuracy of Averages Updated2015-08-14T03:44:57Z Show Answers