Lab assignment Class 1: weighting worksheet Let's say you ... - Users

Lab assignment
Class 1: weighting worksheet
Let’s say you’re interested in farming in contemporary America. The following exercise walks
you through the usual steps you would follow to go about looking into this issue with IPUMS
data. The main skills you should take from this exercise are:
• make a basic table using SPSS
• interpret whether data results are likely to be valid
• identify the appropriate weighting variable and use it
Step 1 Make a table to be sure there are enough cases
You need to have a bare minimum of 100 cases in the category that interests you. If you have
fewer than 100 cases, your results are probably be unreliable. The best way to investigate this
question is to do make a table of the variable of interest. In this case, that’s the FARM variable.
How many individuals in the sample lived on farms in 2000? ________________________
What proportion of the sample lived on farms in 2000?
________________________
SPSS Instructions: Open your data file (the “.sav” file) so that it shows up in the SPSS Data
Editor. Pull down the Analyze menu, select Descriptive Statistics, select Frequencies, and then
select the FARM variable.
Step 2 Redo the analysis with the person weight to get more accurate statistics
You need to redo the frequency table you just made. This time, however, you will use weights.
Using the weights, how many Americans lived on farms in 2000? _____________________
Using the weights, what proportion of Americans lived on farms in 2000? ________________
SPSS Instructions: To turn on weights, open your dataset in the SPSS Data Editor. Pull down
the Data menu and choose “Weight Cases”. Select the “Weight Cases By” button, and choose
the PERWT variable. You should see a “Weight on” button at the bottom righthand corner of
the data editor. At this point you should proceed with the analysis as you did above.
GLOS5900, Sec.002: Work, Family, and Community: Global Perspectives on doing Population History (2004)

Step 3 Using the household weights
Suppose you were interested not in the number of people living on farms, but in the number of
American households that were on farms. In other words, you want a count of farms, not people.
To get this statistic you would need to use the household weight
In order to use household weight, you should be careful to select only one person from each
household to represent that household’s characteristics. Use SPSS to select the first person from
each household (cases where PERNUM=1).
SPSS Instructions: In the Data Editor, pull down the Data menu and choose “Select Cases”. In
the window that pops up, select the second button, labeled “If condition is satisfied”. Click the
“If” button, and type “pernum=1” in the upper right-hand corner of the window that pops up.
Press “Continue” and “OK”. All cases where pernum is not equal to 1 should now have a slash
by them in the Data Editor.
As you did in Step 1 above, you first need to confirm that there are enough farm households to
get reliable results. Produce a frequency table of the farm variable
How many households in the sample were on farms?
_______________
As you did in Step 2 above, you need to apply the household weight variable (HHWT) to get
fully reliable statistics.
Using the household weights, how many American households lived on farms in 2000?
________________
GLOS5900, Sec.002: Work, Family, and Community: Global Perspectives on doing Population History (2004)