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Some options for fractional weights in CROSSTABS

Troubleshooting


Problem

I understand that the CROSSTABS procedure allows users to choose how fractional values for frequency weights are handled. How do I select the option that I want to use?

Resolving The Problem

It is indeed possible to ask CROSSTABS to do things other than round the sums of fractional weights when computing individual cell counts. Technote 1491934 documents the implementation of the decision to round fractional cell counts beginning with SPSS 6.1.2. Automatic rounding remained in force until the introduction of SPSS 11.5. Beginning with Release 11.5, you can use command syntax to choose among several options. Beginning with Release 12, you can specify these options in the Cells dialog box.

The following excerpt from the SPSS 11.5 Syntax Reference Guide shows the documentation of the COUNT subcommand with associated keywords.
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COUNT Subcommand

The COUNT subcommand controls how case weights are handled.

ASIS
The case weights are used as is. However, when Exact Statistics are requested, the accumulated weights in the cells are either truncated or rounded before computing the exact test statistics.

CASE
The case weights are either rounded or truncated before use.

CELL
The case weights are used as is but the accumulated weights in the cells are either truncated or rounded before computing any statistics.

ROUND
Performs Rounding operation.

TRUNCATE
Performs Truncation operation.
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Here are some examples illustrating the use of the new command syntax options.

Example 1

CROSSTABS
/TABLES = a BY b
/COUNT = CASE TRUNCATE.

In this example, the user asks for a two-way crosstabulation of the variables A and B. The cell counts within the table are determined by summing the integer values that result from truncating fractional case weights.

Example 2

CROSSTABS
/TABLES = a BY b BY c
/STATISTIC = CHISQ
/METHOD = EXACT TIMER(5)
/COUNT = CELL ROUND.

In this example, theuser asks for a three-way crosstabulation of the variables A, B, and C. The user also requests the computation of an exact Chi-square test statistic. The COUNT subcommand instructs the procedure to sum noninteger values within each cell and then round the sums. These are the default settings for the COUNT subcommand.

As with all other procedures, weights are applied using the WEIGHT command outside of the procedure.

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Historical Number

31551

Document Information

Modified date:
16 April 2020

UID

swg21479712