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

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Stata 11 Sample Session Section 2 – Restructuring Data Files – Table Lookup & Aggregation 22. Click on Ok . The statements we need are detailed in the table below. Numeric value If statement 1 ca4 == 1 & ca3 >=10 .84 ca4 == 2 & (ca3 >=10 & ca3 =20 .6 ca3 =10 replace ae = .84 if ca4==2 & ca3 >=10 & ca3 =20 replace ae = .6 if ca3 < 10 label variable ae "Adult equivalents" To verify that the new adult equivalent variable, ae, has been calculated, display a frequency table for it. 1. From the menus click on Statistics..then Summaries, tables & tests then Tables then One-way tables The tabulate1 - One-way Tables dialog box opens. 2. Select the variable name ae in the Categorical Variables box which is found under the tab labeled Main. 3. Check the box ✓ next to Treat missing values like other values 68
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 69
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STATA 11 for Windows SAMPLE SESSION - Food Security Group ...

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