OBJECTIVES Last lecture we covered: 1. Which is the preferred measure? Mean or Median 2. Shape MeeasuuessCeentallTendeency 3. Measure off PPosiittiionPercenttiille> 4. Measures of variation MODE MEDIAN MEAN How to compute mean? Data Raw Data Example 3.1 Grouped Data (page 133) In the form of Distribution Examples 3.2, 3.3, 3.4,tal Example 3.7 3.5 Example 3.6 (page 136) (pages 133, 134,135 )age 135) Median Salaryby C ity - Job: Family ian c Doctor (Canada) Which is the preferred measure? Mean or Median Page 139 1 www.notesolution.com Illustration 1 Illustration 2 The following data represents the prices of houses sold laThe following data represents the prices of houses sold in a particular neighbourhood. The data is: last week in a particular neighbourhood. The data is: $240,000 2250,0260,0265,000 $240,000 245,000 250,000 260,000 465,000 Mean house price = $252,000 Mean house price = $292,000 You would get the impression as to the size and type of thYou would get the ipression as to the size ype of house ihe neibourhood.h d the typical house in the neighbourhood. Median house price = $250,000 Median house price = $250,000 Note: The median didnt change You would get the same impression as to the size and type You would get the different impression as to the size and typical house in the neighbourhood. type of the typical house in the neighbourhood. If the mean and median are, then the mean will give the correct impression and is the If the mean and median areOT CLOSE, preferred measure. then the median will give the correct impression Median and Mean Two issues The median is the middle of a distribution: half the scores are above the median and half are below the median. 1. Median is less sensitive to extreme The median is less sensitive to extreme scores scores than the mean and this makes it a 2. How do we conclude that the mean better measure than the mean for highly and median are close or not close? skewed distributions. The median income is usually more informative than the mean income, for example How do we conclude that the How do we conclude that the mean and median are close or mean and median are close or noot closee? nottclosse?? We need some rules. 10% Rule Heuristic Rule The Ten Percent Rule is a general rule of thumb 2 www.notesolution.com

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