Chapter 8 Section 2

# Chapter 8 Section 2 - 8.2 Measures of Central Tendency In...

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8.2 Measures of Central Tendency In this section, we will study three measures of central  tendency: the mean, the median and the mode. Each of  these values determines the “center” or middle of a set of  data.

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Measures of Center Mean Most common Sum of the numbers divided by number of numbers Notation:   Example: The salary of 5 employees in thousands) is:  14, 17, 21, 18, 15 Find the mean: Sum = (14 + 17+21+18+15)=85 Divide 85 by 5 = 17. Thus, the average salary is 17,000 dollars. = = 1 n i i X X n
The Mean as Center of Gravity  We will represent each data value on a “teeter-totter”. The  teeter-totter serves as number line.  You can think of each point's deviation from the mean as the  influence the point exerts on the tilt of the teeter totter. Positive  values push down on the right side; negative values push down  on the left side. The farther a point is from the fulcrum, the  more influence it has. Note that the mean deviation of the scores from the mean is  always zero. That is why the teeter totter is in balance when the  fulcrum is at the mean. This makes the mean the  center of  gravity for all the data points.

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Data balances at 17. Sum of the deviations from mean equals zero. (-3 + -2 + 0 + 1 + 4 = 0 ) .
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Chapter 8 Section 2 - 8.2 Measures of Central Tendency In...

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