1. Stat 217 – Day 8 Quantitative Data cont (Topic 8 – Measures of Center) Have Day 7 Handout and calculators handy

2. Last Time – Quantitative Data You should try to anticipate/predict variable behavior based on the context Graphs: dotplots, stemplots (Act 7-3, 7-4) Checklist of features to comment on:  Shape (symmetric vs. skewed, clusters, other)  Outliers and other unusual observations  …

3. Topic 7 ABCDEFABCDEF cost of your last hair cut number of siblings number of headsnumber of states you’ve visited your heights your rating values of statistics Symmetric Skewed to the leftslightly Skewed to the right

4. Guesses of my age 15 symmetric, 1 skewed left, 6 skewed right Other interesting features?

5. Checklist of important features (p. 121) Center  Easy with symmetric distributions  How decide when skewed? Spread or variability  Consistency Outliers  Identify and consider explanations!  Other unusual features

6. Activity 7-2 (p. 121) Weights of 2008 Men’s Olympic Rowing Team

7. Activity 7-2 www.abc.net.au/olympics/2008/sports/rowing/basics.htm

8. Activity 7-5 (p. 127) Another good graph: histogram  Especially useful for larger data sets

9. Histogram applet

10. Rowers’ weights What do you learn from these graphs?

11. Topic 8 – Measures of Center (a) Observational units? EV? RV? (b) Which section tends to get more sleep? Def: Mean, median Mean = (4+4.75+5+5+6+6+6+6+6.25+6.25+6.5+7+7+7+7+8+8.5)/17=6.25 hrs

12. Whole team Mean197.96 Median205 Whole teamWithout coxswain With max weight at 329 With max weight at 2229 Mean197.96201.17205.33284.5 Median205207 Activity 8-4 2008 Data (25 rowers) 197.96 lbs 205 lbs Day 7 Handout: Using technology to produce dotplot Dotplot summaries applet Type in data values Copy and Paste from file

13. Activity 8-2 (a) Median prize amount  $875 (b) How will mean compare? $131,478

14. Summary Mean and median are both measures of “center”  Median = “typical” value  Mean = “balance point” of distribution Median is resistant to outliers, mean is not For Thursday:  Activities 8-3, 8-5 (with applet, find data files and applets in Blackboard > Course Materials)  No pre-lab (review Activity 5-5)