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Chapter 3

Measures of Central Tendency. Chapter 3. Prepared by Elizabeth Jacobs, Ph.D. Glendale Community College, Arizona. Sometimes we need ONE NUMBER to describe a distribution: Mode = most frequent score Median = Middle Score Mean = Average = m = S X N For X =

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Chapter 3

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  1. Measures of Central Tendency Chapter 3 Prepared by Elizabeth Jacobs, Ph.D. Glendale Community College, Arizona

  2. Sometimes we need ONE NUMBER • to describe a distribution: • Mode = most frequent score • Median = Middle Score • Mean = Average = m = SX • N • For X = • 10,10,10,10,10,9,9,9,9,9,8,8,8,8,8,8,7,7,7,6,6,6,5,5,4,2,2,1 • Calculate the Mode, Median, and Mean

  3. For a Regular Frequency Distribution: m = S fX • N • XffX • 10 5 50 • 9 5 45 • 8 6 48 • 7 3 21 • 6 3 18 • 5 2 10 • 4 1 4 • 3 0 0 • 2 2 4 • 1 1 1 • 0 0 0 • N = 28 S fX = 201 • SfX = 201 = 7.18 • N 28 Greek = population value Practice: Pages 81-82, # 8 and 9

  4. Mean: • Takes all scores into account • A change in one score = a change in the mean • Adding or subtracting from each score, adds or subtracts that number from the mean. Good for Not Good for

  5. SAT Scores 500

  6. Picturing Distributions

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