2.4 MEASURES OF CENTRAL TENDENCY 
        (value at the center or middle of a data set)

MEAN     (arithmetic mean)
        The Sum of the Scores divided by the number of scores

   =  sample mean

 
    =  Population mean
 
 

    #2
 

 
 
 
 

    #6        Students  Versus  Faculty

 
 
 
 

MEDIAN         middle value,   ** arrange in order  **

                        You may use calculator to sort

          If  n is odd --  exact middle
          If  n is even -- mean of middle 2 numbers
 
 

    #2
 
 
 
 

    #6
 
 
 
 
 
 

MODE      Most frequent
            Sometimes   bimodal or multimodal or no mode

    #2
 

    #6

MIDRANGE 

    #2
 

    #6
 
 

ROUNDING RULE
        1 more decimal place than in original numbers
            and round off only on the final answer
 

MEAN FROM FREQUENCY TABLE
 
 
                                        x - Class Mark
                                        f - frequency

    #14
 
Age Class Mark - x Students x*f 
0-2   23  
3-5   33  
6-8   63  
9-11   68  
12-14   19  
15-17   10  
18-20   1  
21-23   0  
 
 
 

COMPARE MIDDLE MEASURES  - Table 2-6  pg. 68
 
 
              MEAN MEDIAN MODE
Mr. Ly 90 90 94 95 96 100      
Ms Meanor 52 68 95 95 95 98      
Ms Interpret 74 79 96 98 99        
 

 Each claimed his/her class "on average" did best.  How?

SKEWNESS    pg. 69