Fixed misleading results in the Kruskal-Wallis test

[pspp] / doc / statistics.texi

diff --git a/doc/statistics.texi b/doc/statistics.texi
index c0e6a1c084d190fdad0a055bec2517d0c034228f..01976e27c950fa4ef21087dc40e0fadbd668a3ee 100644 (file)
--- a/doc/statistics.texi
+++ b/doc/statistics.texi
@@ -678,12 +678,8 @@ The keyword @subcmd{ALL} is the union of @subcmd{DESCRIPTIVES} and @subcmd{XPROD
 CROSSTABS
         /TABLES=@var{var_list} BY @var{var_list} [BY @var{var_list}]@dots{}
         /MISSING=@{TABLE,INCLUDE,REPORT@}
-        /WRITE=@{NONE,CELLS,ALL@}
         /FORMAT=@{TABLES,NOTABLES@}
-                @{PIVOT,NOPIVOT@}
                 @{AVALUE,DVALUE@}
-                @{NOINDEX,INDEX@}
-                @{BOX,NOBOX@}
         /CELLS=@{COUNT,ROW,COLUMN,TOTAL,EXPECTED,RESIDUAL,SRESIDUAL,
                 ASRESIDUAL,ALL,NONE@}
         /COUNT=@{ASIS,CASE,CELL@}
@@ -728,8 +724,6 @@ tables and statistics.  When set to @subcmd{REPORT}, which is allowed only in
 integer mode, user-missing values are included in tables but marked with
 a footnote and excluded from statistical calculations.
 
-Currently the @subcmd{WRITE} subcommand is ignored.
-
 The @subcmd{FORMAT} subcommand controls the characteristics of the
 crosstabulation tables to be displayed.  It has a number of possible
 settings:
@@ -737,22 +731,11 @@ settings:
 @itemize @w{}
 @item
 @subcmd{TABLES}, the default, causes crosstabulation tables to be output.
-@subcmd{NOTABLES} suppresses them.
-
-@item
-@subcmd{PIVOT}, the default, causes each @subcmd{TABLES} subcommand to be displayed in a
-pivot table format.  @subcmd{NOPIVOT} causes the old-style crosstabulation format
-to be used.
+@subcmd{NOTABLES}, which is equivalent to @code{CELLS=NONE}, suppresses them.
 
 @item
 @subcmd{AVALUE}, the default, causes values to be sorted in ascending order.
 @subcmd{DVALUE} asserts a descending sort order.
-
-@item
-@subcmd{INDEX} and @subcmd{NOINDEX} are currently ignored.
-
-@item
-@subcmd{BOX} and @subcmd{NOBOX} is currently ignored.
 @end itemize
 
 The @subcmd{CELLS} subcommand controls the contents of each cell in the displayed
@@ -862,6 +845,59 @@ Approximate T is not calculated for symmetric uncertainty coefficient.
 
 Fixes for any of these deficiencies would be welcomed.
 
+@subsection Crosstabs Example
+
+@cindex chi-square test of independence
+
+A researcher wishes to know if, in an industry, a person's sex is related to
+the person's occupation.  To investigate this, she has determined that the
+@file{personnel.sav} is a representative, randomly selected sample of persons.
+The researcher's null hypothesis is that a person's sex has no relation to a
+person's occupation. She uses a chi-squared test of independence to investigate
+the hypothesis.
+
+@float Example, crosstabs:ex
+@psppsyntax {crosstabs.sps}
+@caption {Running crosstabs on the @exvar{sex} and @exvar{occupation} variables}
+@end float
+
+The syntax in @ref{crosstabs:ex} conducts a chi-squared test of independence.
+The line @code{/tables = occupation by sex} indicates that @exvar{occupation}
+and @exvar{sex} are the variables to be tabulated.  To do this using the @gui{}
+you must place these variable names respectively in the @samp{Row} and
+@samp{Column} fields as shown in @ref{crosstabs:scr}.
+
+@float Screenshot, crosstabs:scr
+@psppimage {crosstabs}
+@caption {The Crosstabs dialog box with the @exvar{sex} and @exvar{occupation} variables selected}
+@end float
+
+Similarly, the @samp{Cells} button shows a dialog box to select the @code{count}
+and @code{expected} options.  All other cell options can be deselected for this
+test.
+
+You would use the @samp{Format} and @samp{Statistics}  buttons to select options
+for the @subcmd{FORMAT} and @subcmd{STATISTICS} subcommands.  In this example,
+the @samp{Statistics} requires only the @samp{Chisq} option to be checked.  All
+other options should be unchecked.  No special settings are required from the
+@samp{Format} dialog.
+
+As shown in @ref{crosstabs:res} @cmd{CROSSTABS} generates a contingency table
+containing the observed count and the expected count of each sex and each
+occupation.  The expected count is the count which would be observed if the
+null hypothesis were true.
+
+The significance of the Pearson Chi-Square value is very much larger than the
+normally accepted value of 0.05 and so one cannot reject the null hypothesis.
+Thus the researcher must conclude that a person's sex has no relation to the
+person's occupation.
+
+@float Results, crosstabs:res
+@psppoutput {crosstabs}
+@caption {The results of a test of independence between @exvar{sex} and @exvar{occupation}}
+@end float
+
+
 @node FACTOR
 @section FACTOR
 
@@ -1598,9 +1634,10 @@ arbitrary number of populations.  It does not assume normality.
 The data to be compared are specified by @var{var_list}.
 The categorical variable determining the groups to which the
 data belongs is given by @var{var}. The limits @var{lower} and
-@var{upper} specify the valid range of @var{var}. Any cases for
-which @var{var} falls outside [@var{lower}, @var{upper}] are
-ignored.
+@var{upper} specify the valid range of @var{var}.
+If @var{upper} is smaller than @var{lower}, the PSPP will assume their values
+to be reversed. Any cases for which @var{var} falls outside
+[@var{lower}, @var{upper}] are ignored.
 
 The mean rank of each group as well as the chi-squared value and
 significance of the test are printed.