1. Fundamental Statistics for the Behavioral Sciences, 5th edition David C. Howell Chapter 4 Measures of Central Tendency © 2003 Brooks/Cole Publishing Company/ITP

2. 2Chapter 4 Central Tendency Major Points ModeMode MedianMedian MeanMean Relative advantages and disadvantagesRelative advantages and disadvantages Review questionsReview questions

3. 3Chapter 4 Central TendencyMode The most common valueThe most common value There may be severalThere may be several Bimodal distribution has two distinct modes.Bimodal distribution has two distinct modes.

4. 4Chapter 4 Central TendencyMedian Center value in an ordered seriesCenter value in an ordered series XAverage of two center values for an even number of points Median locationMedian location Xlocation of central value Xdefined as (N + 1)/2

5. 5Chapter 4 Central TendencyMean What we normally call the “average”What we normally call the “average” Denoted as “xbar”Denoted as “xbar” Calculated asCalculated as This will be our most common statisticThis will be our most common statistic

6. 6Chapter 4 Central Tendency Relative Advantages ModeMode XThe most frequently obtained score XNot influenced by extreme scores MedianMedian XLittle influenced by extreme scores XReasonable estimate of what most people mean by the center of a distribution Cont.

7. 7Chapter 4 Central Tendency Advantages --cont. MeanMean XMost common statistic XEasily manipulated algebraically XGood statistical properties

8. 8Chapter 4 Central TendencyDisadvantages ModeMode XMay not represent a large proportion of the scores XIgnores extreme values completely MedianMedian XSlightly less desirable statistical properties than mean XMay not be good to ignore extreme values Cont.

9. 9Chapter 4 Central Tendency Disadvantages --cont. MeanMean XToo easily influenced by extreme scores XRequires some faith in interval properties of measurement.

10. 10Chapter 4 Central Tendency Review Questions List the advantages and disadvantages of each measure of central tendency.List the advantages and disadvantages of each measure of central tendency. Which measure would you use if you wanted to discuss performance on the next class test?Which measure would you use if you wanted to discuss performance on the next class test? If your class contains many older students, what measure of average income is appropriate?If your class contains many older students, what measure of average income is appropriate?