EXERCISE 4 - ANSWER

Compare the number of hours worked per day and racial status. First, generate a table without missing values, then generate one with missing values.

Type in the following command:

tab race, sum(hours_v)

This generates the following table without including the missing values:

         19 | Summary of 3d:hours worked average 
:population | day 
      group |     Mean Std.        Dev.     Freq. 
------------+------------------------------------ 
   01-afric |     7.2407407    3.807157        81 
   02-colou |     4.8333333   4.4072942        12 
   03-india |           9.2   .83666003         5 
   04-white |      5.828125   2.1227316        16 
------------+------------------------------------ 
      Total |         6.875   3.7024642       114

Now type in the following command to include the missing values:

tab race, sum(hours_v) missing

This generates the following table, which includes the missing values:

         19 | Summary of 3d:hours worked average 
:population | day 
      group |      Mean Std.       Dev.     Freq. 
------------+------------------------------------ 
   01-afric |      7.2407407   3.807157        81 
   02-colou |      4.8333333  4.4072942        12 
   03-india |            9.2  .83666003         5 
   04-white |       5.828125  2.1227316        16 
          . |              6  2.8284271         2 
------------+------------------------------------ 
      Total |      6.8599138  3.6813704       116 

Notice, when comparing the two tables, that the two missing values do alter the average mean value somewhat.