Chapter 3 Numerical Descriptions of Data Section 3.1 Measures of Center Mean Add up all data values, then divide by the total number of data values. Example 1+2+3+4+5 5 =3 ROUNDING RULE: round to one more decimal place than the highest number of decimal places contained in the data Weighted Mean Multiply each data value by its “weight” then divide by the sum of the weights. Think “per what?” to determine what the weight is. Example: Class Hours Grade Weight Math 3 B 3 English 3 A 4 History 3 C 2 Science 3 A 4 PE 3 F 0 ℎ = 3 3 + 3 4 + 3 2 + 3 4 + 3(0) = 15 9 + 12 + 6 + 12 + 0 39 = = = 2.6 15 15 Solution: a. 3 b. 2.5 Solution: no mode, unimodal, bimodal Section 3.2 Measures of Dispersion Calculator Directions Press STAT Press edit In L1 insert data values. If you need to clear data, press up to highlight L1, press clear (not delete), and press down. Press 2nd quit (mode) Press STAT Arrow over to CALC Press 1-Var Stats On the home screen, press 2nd L1 (1) Press enter You will then see a list of items. = = = To find the variance, you will square the standard deviation. If you scroll down you will see the max, min, and median.