Basic Descriptive Statistics

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This is a presentation for my Env. Chem students regarding the basic statistics they will be using in class throughout the year.

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Basic Descriptive Statistics

  1. 1. Basic Descriptive Statistics Mr. Siko Clarkston HS
  2. 2. Why?  Descriptive statistics do just that: Describe Data!  What we’ll cover in this slidecast – Mean (average) – Median – Mode – Range
  3. 3. Mean Fancy Formula µ = ΣX/N
  4. 4. Mean Fancy Formula  What this means: add µ = ΣX/N up all your data, then divide by the number of data points
  5. 5. Mean Sample data: 98cm 76cm 82cm 54cm 90cm
  6. 6. Mean Sample data: How to calculate: 98cm 76cm 98+76+82+54+90 = 82cm 400cm 54cm 90cm
  7. 7. Mean Sample data: How to calculate: 98cm 76cm 98+76+82+54+90 = 82cm 400cm 54cm 90cm 400cm/5 = 80cm
  8. 8. Mean Sample data: How to calculate: 98cm 76cm 98+76+82+54+90 = 82cm 400cm 54cm 90cm 400cm/5 = 80cm
  9. 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. 10. Median Sample data: 98cm 76cm 82cm 54cm 90cm
  11. 11. Median Sample data: Rearranged Data: 98cm 54cm 76cm 76cm 82cm 82cm 54cm 90cm 90cm 98cm
  12. 12. Median Sample data: Rearranged Data: 98cm 54cm 76cm 76cm 82cm 82cm 54cm 90cm 90cm 98cm
  13. 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. 14. Median Sample Data: 4ml 8ml 12ml 2ml
  15. 15. Median Sample Data: Rearranged Data: 4ml 2ml 8ml 4ml 12ml 8ml 2ml 12ml
  16. 16. Median Sample Data: Rearranged Data: 4ml 2ml 8ml 4ml 12ml 8ml 2ml 12ml 4 + 8 = 12ml 12/2 = 6ml
  17. 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. 18. Mode Sample Data: 20g 23g 30g 30g 22g 27g 25g 20g 23g 24g 23g 25g 20g 23g
  19. 19. Mode Sample Data: Rearranged Data: 20g 23g 20g 20g 20g 30g 30g 22g 22g 27g 23g 23g 23g 23g 25g 20g 24g 23g 24g 25g 25g 23g 25g 27g 20g 23g 30g 30g
  20. 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. 21. Range Sample data: Rearranged Data: 98cm 54cm 76cm 76cm 82cm 82cm 54cm 90cm 90cm 98cm
  22. 22. Range Sample data: Rearranged Data: 98cm 54cm 76cm 76cm 82cm 82cm 54cm 90cm 90cm 98cm 98cm – 54cm = 44cm
  23. 23. Recap  Mean, Median, Mode, and Range “describe” the data.
  24. 24. Acknowledgements American Chemical Society. (2006). Chemistry in the community: ChemCom (5th ed). New York: W.H. Freeman

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