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Basic Descriptive Statistics

Basic Descriptive Statistics. Dr. Yeh. Why?. Descriptive statistics do just that: Describe Data! What we’ll cover in this slidecast Mean (average) Median Mode Range. Fancy Formula µ = X/N. Mean. Fancy Formula µ = X/N. Mean.

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Basic Descriptive Statistics

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  1. Basic Descriptive Statistics Dr. Yeh

  2. Why? • Descriptive statistics do just that: Describe Data! • What we’ll cover in this slidecast • Mean (average) • Median • Mode • Range

  3. Fancy Formula µ = X/N Mean

  4. Fancy Formula µ = X/N Mean • What this means: add up all your data, then divide by the number of data points

  5. Sample data: 98cm 76cm 82cm 54cm 90cm Mean

  6. Sample data: 98cm 76cm 82cm 54cm 90cm Mean How to calculate: 98+76+82+54+90 = 400cm

  7. Sample data: 98cm 76cm 82cm 54cm 90cm Mean How to calculate: 98+76+82+54+90 = 400cm 400cm/5 = 80cm

  8. Sample data: 98cm 76cm 82cm 54cm 90cm Mean How to calculate: 98+76+82+54+90 = 400cm 400cm/5 = 80cm

  9. Median • The median is the middle data point in a set • To determine the median, sort the data from smallest to largest and find the middle data point

  10. Sample data: 98cm 76cm 82cm 54cm 90cm Median

  11. Sample data: 98cm 76cm 82cm 54cm 90cm Median Rearranged Data: 54cm 76cm 82cm 90cm 98cm

  12. Sample data: 98cm 76cm 82cm 54cm 90cm Rearranged Data: 54cm 76cm 82cm 90cm 98cm Median

  13. Median • If there is an even number of data, there will be two middle points. • To find the median, take the average of those two data.

  14. Sample Data: 4ml 8ml 12ml 2ml Median

  15. Sample Data: 4ml 8ml 12ml 2ml Median Rearranged Data: 2ml 4ml 8ml 12ml

  16. Sample Data: 4ml 8ml 12ml 2ml Rearranged Data: 2ml 4ml 8ml 12ml Median 4 + 8 = 12ml 12/2 = 6ml

  17. Mode • The mode is the most frequently occurring data point. • To find the mode, arrange the data from smallest to largest, and then determine which amount occurs most often.

  18. Sample Data: 20g 23g 30g 30g 22g 27g 25g 20g 23g 24g 23g 25g 20g 23g Mode

  19. Sample Data: 20g 23g 30g 30g 22g 27g 25g 20g 23g 24g 23g 25g 20g 23g Rearranged Data: 20g 20g 20g 22g 23g 23g 23g 23g 24g 25g 25g 27g 30g 30g Mode

  20. Range • The range is the distance between the smallest and largest data point. • To calculate, determine the smallest data point and the largest data point, then subtract the smallest from the largest.

  21. Sample data: 98cm 76cm 82cm 54cm 90cm Range Rearranged Data: 54cm 76cm 82cm 90cm 98cm

  22. Sample data: 98cm 76cm 82cm 54cm 90cm Rearranged Data: 54cm 76cm 82cm 90cm 98cm Range 98cm – 54cm = 44cm

  23. Recap • Mean, Median, Mode, and Range “describe” the data.

  24. Acknowledgements American Chemical Society. (2006). Chemistry in the community: ChemCom (5th ed). New York: W.H. Freeman

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