STATA 11 for Windows SAMPLE SESSION - Food Security Group ...

Stata 11 Sample Session Section 2 – Restructuring Data Files – Table Lookup & Aggregation
Replace “missing values” with a
mean value
4. Click on the copy button, switch to the do-file
editor, paste the command, switch back to the
dialog box and click on the Ok button.
The Stata command is:
tabulate ae, missing
You should see there are 1524 total cases. Ideally there
should be four values represented in the table —1, .72,
.84, and .60— and no missing cases. You can see we
have nine missing cases. This tells us that our data file is
missing either the age or the sex for nine people. This
problem should have been identified during the cleaning
process. At this point it would be ideal for the researcher
to go back to the original questionnaires to determine the
reason why these data are missing. Since we can't do
this, we will use an alternative method.
If we leave these values missing, the total adult
equivalents of those households will appear to be slightly
smaller, which may distort the results. We could avoid
this problem by eliminating the households with missing
information from our analysis, but then we can't use the
information about the food production from those
households. Instead, we will try to make a reasonable
assumption about those nine missing members. We know
that the adult-equivalent values range from a low of .6 for
children to a high of 1.0 for adult males, which is not a
very wide range. We can determine the mean adultequivalent
value for the whole sample and use that value
to fill in the missing data. To find out the average adultequivalent
value for our sample...
1. Statistics then Summaries, tables and tests
then Summary and Descriptive Statistics then
Summary Statistics
2. Select the variable: ae
3. Don’t forget to copy the command into the do-file
editor, then click on the Ok button
The Stata command is:
summarize ae
We can see that the mean value of ae for all individuals
is .79, with a standard deviation of only .17. We will
assume that the nine individuals with missing age or sex
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