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Crosstabs

Statistical
Package
for the
Social
Sciences
CROSSTABS

CROSSTABS is an SPSS procedure that
CROSSTABULATES two variables, thus displaying their
relationship in tabular form. While FREQUENCIES is a
useful procedures for summarizing information about one
variable, CROSSTABS generates information about
bivariate relationships.
Because CROSSTABS creates a row for each value in one
variable and a column for each value in the other, the
procedure is not suitable for continuous
variables that assume many values. CROSSTABS is designed
for discrete variablesusually those measured on
nominal or ordinal scales.
CROSSTABS creates a table that contains a cell for
every combination of the categories in the two variables.
Inside each cell is the number of cases that fit that
particular combination of responses. SPSS can also report
the row, column, and total percentages for each cell of
the table.

This is an example of CROSSTAB output from
SPSS:
      C R O S S T A B U L A T I O N O F    CDBG8089 NET CHANGE IN CDBG FUNDS, 198089 BY REGION CENSUS REGIONS COUNT ROW PCT I NORTH NORTH SOUTH WEST PUERTO ROW COL PCT I EAST CENTRAL RICO TOTAL TOT PCT I 1 I 2 I 3 I 4 I 5 I DBG8089 +++++++ 1 I 38 I 33 I 51 I 61 I 4 I 187 INCREASED I 20.3 I 17.6 I 27.3 I 32.6 I 2.1 I 23.0 I 19.3 I 16.2 I 23.4 I 33.7 I 33.3 I I 4.7 I 4.1 I 6.3 I 7.5 I .5 I ++++++ 3 I 159 I 171 I 167 I 120 I 8 I 625 DECREASED I 25.4 I 27.4 I 26.7 I 19.2 I 1.3 I 77.0 I 80.7 I 83.8 I 76.6 I 66.3 I 66.7 I I 19.6 I 21.1 I 20.6 I 14.8 I 1.0 I ++++++ COLUMN 197 204 218 181 12 812 TOTAL 24.3 25.1 26.8 22.3 1.5 100.0
NUMBER OF MISSING OBSERVATIONS = 49


This is the general, abstract form of CROSSTABS
output

Independent
Variable

Dependent
Variable

category 1

category 2

. . category k

Totals

Category 1

Table entries consist of
frequencies, or percentages, or both.
Intersections of rows and columns are called
"cells."

row 1

Category 2

row 1

.
.
Category j

.
.
row j

Totals

N

N

N

Grand N

Percents

100.0

100.0

100.0

100.0

 The percentage entries in the cells should sum
to 100% at the bottom of the table if CELLS=COLUMN
(print column percentages) is requested.

CROSSTABS

produces a table with one variable at the side
and another at the top, a "crosstabulation"

 CROSSTABS:
[varlist] list of variable names,
joined with the SPSS keyword BY
 /CELLS= [specifies what values are
printed in the cells of the table]
 main ones are COUNT of cases and % by
ROW, COLumn, and TOTAL number
of cases
 Asking for percents by columns is desired if
you lay out the table with the independent variable
in the columns (i.e., across the top)
 /STATISTICS: prints requested measures of
association

 Subcommands
 CELLS= Should you use COLUMN or ROW?
 It depends on which of your variables you
regard as "independent."
 Always compute percentages using the N's in the
marginals of whichever variable you regard as
independent.
 Conventionally, the column variable (across the
top) is the independent variable, which calls for
COLUMN.
 STATISTICS
 CROSSTABS generates many different statistics,
some of which are more useful than others.
 STATISTICS= CHISQ PHI CC will generate
these statistics
 chisquare (X^{2})
tests for independence between nominal
variables
phi (2x2 tables) and Cramer's V
(nxn tables)measure of
association based on X^{2}
Contingency Coefficient, C

 Consider CROSSTABS commands for today's assignment
using the vote92 file. You'll have to put in
the right variables for vote96
 CROSSTABS V2 BY V8 V125 / V2 BY V8 BY V125
 /CELLS=COUNT COLUMN / STATISTICS= [names of
statistics here]



Conventions and advice concerning CROSTABS
 By convention, the independent variable is
arranged across the top of the table, unless
number of categories or size of space prohibit.

 ALWAYS, percentages are computed within the
categories of the independent variable  as shown
in the sample table  and the number of cases on
which the percentages are based is always given.

 Try to avoid cluttering a table with unnecessary
information  e.g., percentages by rows AND columns 
even percentages AND frequencies in the same cell.

 Follow format in professional journals for
constructing tables; it is bad form to submit raw
printout from SPSS runs as tables in course papers.

 Limitations of CROSSTABS print format
 CROSSTABS tables in SPSS are limited to 10
categories for the independent variable (across the
top) on standardsize (wide) paper.
 There is no limitation on the number of categories
for the dependent variable  down the side.

 Consequences of the limitation
 Tables with more than 10 categories for the
independent variable will be "wrapped around" and
printed as a "continuation" of the first table.

 Consider this example:
 Supposing an AGE variable has values ranging
from 17 to 99 and an INCOME variable has 20 coding
categories.
 If one specified CROSSTABS INCOME BY AGE, only
the first 10 of AGE's values could fit across the
top of the page, and a continuation table would be
printed on another page.
 However, the command CROSSTABS AGE BY INCOME
would place AGE along the side, allowing it to
print out in full on one table (if one really
wanted age by exact years).

 The AGE variable could also be "recoded" into
fewer categories with handled by using the RECODE
command in SPSS.
 RECODE can be used either to change or to
combine codes assigned to variables in an SPSS
file.
 For example, V8 is a 7 category measure of
party identification, ranging from 0 to 6.
 These scores can be "recoded" to a 3point
scale as follows:
 RECODE V8 (0=1) (2,4=3) (6=5)
 When placed before the CROSSTABS command,
RECODE will change the variable into a trichotomy:
1=Democrats, 3=Independents, and
5=Republicans.
