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Chapter 3 Numerical Descriptions of Data Section 3.1 Measures of Center Mean ο΅ Add up all data values, then divide by the total number of data values. ο΅ 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 ο΅ Multiply each data value by its “weight” then divide by the sum of the weights. Think “per what?” to determine what the weight is. ο΅ 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 ππππβπ‘ππ ππππ = πΊππ΄ 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 ο΅ Press STAT ο΅ Press edit ο΅ In L1 insert data values. If you need to clear data, press up to highlight L1, press clear (not delete), and press down. ο΅ Press 2nd quit (mode) ο΅ Press STAT ο΅ Arrow over to CALC ο΅ Press 1-Var Stats ο΅ On the home screen, press 2nd L1 (1) ο΅ Press enter ο΅ You will then see a list of items. ο΅ π₯ = ππππ ππ₯ = π πππππ π π‘ππππππ πππ£πππ‘πππ ππ₯ = ππππ’πππ‘πππ π π‘ππππππ πππ£πππ‘πππ ο΅ To find the variance, you will square the standard deviation. ο΅ If you scroll down you will see the max, min, and median.