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Section 1.1 Part 4

Section 1.1 Part 4. AP Statistics September 8, 2008 CASA. Using Percents. It is sometimes difficult to compare the “straight” numbers. For example:

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Section 1.1 Part 4

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  1. Section 1.1Part 4 AP Statistics September 8, 2008 CASA

  2. Using Percents • It is sometimes difficult to compare the “straight” numbers. For example: • Ty Cobb in his 24 year baseball career had 4,189 hits. Pete Rose also played for 24 years but he collected 4,256 hits. Was Pete Rose a better batter than Ty Cobb? AP Statistics, Section 1.1, Part 4

  3. Using Percents • Ty Cobb had a career batting average of .366. (He got a hit 36.6% of the time) • Pete Rose had a career batting average of .303. • Comparing the percentage, we get a clearer picture. AP Statistics, Section 1.1, Part 4

  4. Relative Frequency • When constructing a histogram we can use the “relative frequency” (given in percent) instead of “count” or “frequency” • Using relative frequency allows us to do better comparisons. • Histograms using relative frequency have the same shape as those using count. AP Statistics, Section 1.1, Part 4

  5. Finding Relative Frequency • For each count in a class, divide by the total number of data points in the data set. • Convert to a percentage. AP Statistics, Section 1.1, Part 4

  6. Finding Relative Frequency AP Statistics, Section 1.1, Part 4

  7. Finding Relative Frequency AP Statistics, Section 1.1, Part 4

  8. Histograms AP Statistics, Section 1.1, Part 4

  9. Finding Cumulative Frequency AP Statistics, Section 1.1, Part 4

  10. Finding Relative Cumulative Frequency AP Statistics, Section 1.1, Part 4

  11. Percentiles • “The pth percentile of a distribution is the value such that p percent of the observations fall at or below it.” • If you scored in the 80th percentile on the SAT, then 80% of all test takers are at or below your score. AP Statistics, Section 1.1, Part 4

  12. Percentiles • It is easy to see the percentiles at the breaks. • “A 64 year old would be at the 93rd percentile.” • What do you do for a 57 year old? AP Statistics, Section 1.1, Part 4

  13. Ogives (o-JIVE) or “Relative Cumulative Frequency Graph” AP Statistics, Section 1.1, Part 4

  14. Time Plots • Time (measured in seconds, days, months, years, etc.) is always on the x-axis. • Use time plots to see trends related to time like… • Seasonal variation • Growth trends AP Statistics, Section 1.1, Part 4

  15. Assignment • Exercises 1.19 – 1.29 odd, The Practice of Statistics. AP Statistics, Section 1.1, Part 4

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