PPPM
613

Planning Analysis:
Class 13: SPSS II--Basic Procedures

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Frequencies

The Frequencies procedure provides statistics and graphical displays that are useful for describing many types of variables. For a first look at your data, the Frequencies procedure is a good place to start.

For a frequency report and bar chart, you can arrange the distinct values in ascending or descending order or order the categories by their frequencies. The frequencies report can be suppressed when a variable has many distinct values. You can label charts with frequencies (the default) or percentages.

Recoding

The Recode procedure allows you to group values in a variable. You can recode values into the same variable, or into a different variable. Recode into Different Variables reassigns the values of existing variables or collapses ranges of existing values into new values for a new variable. For example, you could collapse salaries into a new variable containing salary-range categories.

Crosstabs

The Crosstabs procedure forms two-way and multiway tables and provides 22 tests and measures of association for two-way tables. The structure of the table and whether categories are ordered determine what test or measure to use.

Crosstabs’ statistics and measures of association are computed for two-way tables only. If you specify a row, a column, and a layer factor (control variable), SPSS forms one panel of associated statistics and measures for each value of the layer factor (or a combination of values for two or more control variables). For example, if GENDER is a layer factor for a table of MARRIED (yes, no) against LIFE (is life exciting, routine, or dull), the results for a two-way table for the females are computed separately from those for the males and printed as panels following one another.

Sort Cases

This dialog box sorts cases (rows) of the data file based on the values of one or more sorting variables. You can sort cases in ascending or descending order.

If you select multiple sort variables, cases are sorted by each variable within categories of the prior variable on the Sort list. For example, if you select GENDER as the first sorting variable and MINORITY as the second sorting variable, cases will be sorted by minority classification within each gender category.

For string variables, uppercase letters precede their lowercase counterparts in sort order. For example, the string value "Yes" comes before "yes" in sort order.

Split File

Split File splits the data file into separate groups for analysis, based on the values of one or more grouping variables. If you select multiple grouping variables, cases are grouped by each variable within categories of the prior variable on the Groups Based On list. For example, if you select GENDER as the first grouping variable and MINORITY as the second grouping variable, cases will be grouped by minority classification within each gender category.

  • You can specify up to eight grouping variables.
  • Each eight characters of a long string variable (string variables longer than 8 characters) counts as a variable toward the limit of eight grouping variables.
  • Cases should be sorted by values of the grouping variables, in the same order as variables are listed in the Groups Based On list. If the data file isn’t already sorted, select Sort the file by grouping variables.

Select Cases

Select Cases provides several methods for selecting a subgroup of cases based on criteria that include variables and complex expressions. You can also select a random sample of cases. The criteria used to define a subgroup can include:

  • Variable values and ranges
  • Date and time ranges
  • Case (row) numbers
  • Arithmetic expressions
  • Logical expressions
  • Functions

Unselected Cases. You can filter or delete cases that don’t meet the selection criteria. Filtered cases remain in the data file but are excluded from analysis. SPSS creates a filter variable, FILTER_$, to indicate filter status. Selected cases have a value of 1; filtered cases have a value of 0. Filtered cases are also indicated with a slash through the row number in the Data Editor. To turn filtering off and include all cases in your analysis, select All cases.

Deleted cases are removed from the data file and cannot be recovered if you save the data file after deleting the cases.

Compute

Compute Variable computes values for a variable based on numeric transformations of other variables.

  • You can compute values for numeric or string variables.
  • You can create new variables or replace the values of existing variables. For new variables, you can also specify the variable type and label.
  • You can compute values selectively for subsets of data based on logical conditions.
  • You can use over 70 built-in functions, including arithmetic functions, statistical functions, distribution functions, and string functions.

Meanwhile, you might work through SPSS Exercise 2


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This page maintained by Bob Parker, ©2002
September 26, 2000