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Measures of Dispersion

Measures of Dispersion. Section 12.3. Measures of dispersion describe how the data items are spread out in the data set. Range – the difference between the highest and lowest data values in a data set; indicates the total spread of the data depending only on the

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Measures of Dispersion

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  1. Measures of Dispersion Section 12.3

  2. Measures of dispersion describe how the data items are spread out in the data set. Range – the difference between the highest and lowest data values in a data set; indicates the total spread of the data depending only on the extreme values Standard deviation – a measure dependent on all the data items and found by determining how much each data item differs from the mean (average)

  3. Example Find the range and standard deviation for: 806, 700, 666, 611, 597 Range= highest – lowest = 806 – 597 = 209

  4. Example Find the range and standard deviation for: 806, 700, 666, 611, 597 To calculate the standard deviation, first find the mean.

  5. Example Find the range and standard deviation for: 806, 700, 666, 611, 597 Now, create a table with three columns. Data values are entered in the 1st column, x.

  6. Example Find the range and standard deviation for: 806, 700, 666, 611, 597 Recall: mean = 676 Total is always ZERO! Add the column. What is the total? In the 2nd column subtract the mean from each data item, labeled x –.

  7. Example Find the range and standard deviation for: 806, 700, 666, 611, 597 In the 3rd column square each answer from the 2nd column, labeled (x –)2.

  8. There are two kinds of standard deviation …this is for the POPULATION. Example Find the range and standard deviation for: 806, 700, 666, 611, 597 Standard Deviation S Add this column. S S S S83.73

  9. The End “Facts are stubborn, but statistics are more pliable.”– Mark Twain HOMEWORK 12.3 pg 663 # 1 – 25 every other odd, # 27 – 39 odd

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