1 @node Statistics, Utilities, Conditionals and Looping, Top
4 This chapter documents the statistical procedures that PSPP supports so
7 @c If you add any new commands, then don't forget to remove the entry in
8 @c not-implemented.texi
11 * DESCRIPTIVES:: Descriptive statistics.
12 * FREQUENCIES:: Frequency tables.
13 * CROSSTABS:: Crosstabulation tables.
14 * T-TEST:: Test hypotheses about means.
15 * ONEWAY:: One way analysis of variance.
18 @node DESCRIPTIVES, FREQUENCIES, Statistics, Statistics
25 /MISSING=@{VARIABLE,LISTWISE@} @{INCLUDE,NOINCLUDE@}
26 /FORMAT=@{LABELS,NOLABELS@} @{NOINDEX,INDEX@} @{LINE,SERIAL@}
28 /STATISTICS=@{ALL,MEAN,SEMEAN,STDDEV,VARIANCE,KURTOSIS,
29 SKEWNESS,RANGE,MINIMUM,MAXIMUM,SUM,DEFAULT,
30 SESKEWNESS,SEKURTOSIS@}
31 /SORT=@{NONE,MEAN,SEMEAN,STDDEV,VARIANCE,KURTOSIS,SKEWNESS,
32 RANGE,MINIMUM,MAXIMUM,SUM,SESKEWNESS,SEKURTOSIS,NAME@}
36 The @cmd{DESCRIPTIVES} procedure reads the active file and outputs
38 statistics requested by the user. In addition, it can optionally
41 The VARIABLES subcommand, which is required, specifies the list of
42 variables to be analyzed. Keyword VARIABLES is optional.
44 All other subcommands are optional:
46 The MISSING subcommand determines the handling of missing variables. If
47 INCLUDE is set, then user-missing values are included in the
48 calculations. If NOINCLUDE is set, which is the default, user-missing
49 values are excluded. If VARIABLE is set, then missing values are
50 excluded on a variable by variable basis; if LISTWISE is set, then
51 the entire case is excluded whenever any value in that case has a
52 system-missing or, if INCLUDE is set, user-missing value.
54 The FORMAT subcommand affects the output format. Currently the
55 LABELS/NOLABELS and NOINDEX/INDEX settings are not used. When SERIAL is
56 set, both valid and missing number of cases are listed in the output;
57 when NOSERIAL is set, only valid cases are listed.
59 The SAVE subcommand causes @cmd{DESCRIPTIVES} to calculate Z scores for all
60 the specified variables. The Z scores are saved to new variables.
61 Variable names are generated by trying first the original variable name
62 with Z prepended and truncated to a maximum of 8 characters, then the
63 names ZSC000 through ZSC999, STDZ00 through STDZ09, ZZZZ00 through
64 ZZZZ09, ZQZQ00 through ZQZQ09, in that sequence. In addition, Z score
65 variable names can be specified explicitly on VARIABLES in the variable
66 list by enclosing them in parentheses after each variable.
68 The STATISTICS subcommand specifies the statistics to be displayed:
72 All of the statistics below.
76 Standard error of the mean.
82 Kurtosis and standard error of the kurtosis.
84 Skewness and standard error of the skewness.
94 Mean, standard deviation of the mean, minimum, maximum.
96 Standard error of the kurtosis.
98 Standard error of the skewness.
101 The SORT subcommand specifies how the statistics should be sorted. Most
102 of the possible values should be self-explanatory. NAME causes the
103 statistics to be sorted by name. By default, the statistics are listed
104 in the order that they are specified on the VARIABLES subcommand. The A
105 and D settings request an ascending or descending sort order,
108 @node FREQUENCIES, CROSSTABS, DESCRIPTIVES, Statistics
115 /FORMAT=@{TABLE,NOTABLE,LIMIT(limit)@}
116 @{STANDARD,CONDENSE,ONEPAGE[(onepage_limit)]@}
118 @{AVALUE,DVALUE,AFREQ,DFREQ@}
121 /MISSING=@{EXCLUDE,INCLUDE@}
122 /STATISTICS=@{DEFAULT,MEAN,SEMEAN,MEDIAN,MODE,STDDEV,VARIANCE,
123 KURTOSIS,SKEWNESS,RANGE,MINIMUM,MAXIMUM,SUM,
124 SESKEWNESS,SEKURTOSIS,ALL,NONE@}
126 /PERCENTILES=percent@dots{}
128 (These options are not currently implemented.)
135 /VARIABLES=var_list (low,high)@dots{}
138 The @cmd{FREQUENCIES} procedure outputs frequency tables for specified
140 @cmd{FREQUENCIES} can also calculate and display descriptive statistics
141 (including median and mode) and percentiles.
143 In the future, @cmd{FREQUENCIES} will also support graphical output in the
144 form of bar charts and histograms. In addition, it will be able to
145 support percentiles for grouped data.
147 The VARIABLES subcommand is the only required subcommand. Specify the
148 variables to be analyzed. In most cases, this is all that is required.
149 This is known as @dfn{general mode}.
151 Occasionally, one may want to invoke a special mode called @dfn{integer
152 mode}. Normally, in general mode, PSPP will automatically determine
153 what values occur in the data. In integer mode, the user specifies the
154 range of values that the data assumes. To invoke this mode, specify a
155 range of data values in parentheses, separated by a comma. Data values
156 inside the range are truncated to the nearest integer, then assigned to
157 that value. If values occur outside this range, they are discarded.
159 The FORMAT subcommand controls the output format. It has several
164 TABLE, the default, causes a frequency table to be output for every
165 variable specified. NOTABLE prevents them from being output. LIMIT
166 with a numeric argument causes them to be output except when there are
167 more than the specified number of values in the table.
170 STANDARD frequency tables contain more complete information, but also to
171 take up more space on the printed page. CONDENSE frequency tables are
172 less informative but take up less space. ONEPAGE with a numeric
173 argument will output standard frequency tables if there are the
174 specified number of values or less, condensed tables otherwise. ONEPAGE
175 without an argument defaults to a threshold of 50 values.
178 LABELS causes value labels to be displayed in STANDARD frequency
179 tables. NOLABLES prevents this.
182 Normally frequency tables are sorted in ascending order by value. This
183 is AVALUE. DVALUE tables are sorted in descending order by value.
184 AFREQ and DFREQ tables are sorted in ascending and descending order,
185 respectively, by frequency count.
188 SINGLE spaced frequency tables are closely spaced. DOUBLE spaced
189 frequency tables have wider spacing.
192 OLDPAGE and NEWPAGE are not currently used.
195 The MISSING subcommand controls the handling of user-missing values.
196 When EXCLUDE, the default, is set, user-missing values are not included
197 in frequency tables or statistics. When INCLUDE is set, user-missing
198 are included. System-missing values are never included in statistics,
199 but are listed in frequency tables.
201 The available STATISTICS are the same as available in @cmd{DESCRIPTIVES}
202 (@pxref{DESCRIPTIVES}), with the addition of MEDIAN, the data's median
203 value, and MODE, the mode. (If there are multiple modes, the smallest
204 value is reported.) By default, the mean, standard deviation of the
205 mean, minimum, and maximum are reported for each variable.
207 PERCENTILES causes the specified percentiles to be reported.
208 The percentiles should be presented at a list of numbers between 0
210 The NTILES subcommand causes the percentiles to be reported at the
211 boundaries of the data set divided into the specified number of ranges.
212 For instance, @code{/NTILES=4} would cause quartiles to be reported.
215 @node CROSSTABS, T-TEST, FREQUENCIES, Statistics
221 /TABLES=var_list BY var_list [BY var_list]@dots{}
222 /MISSING=@{TABLE,INCLUDE,REPORT@}
223 /WRITE=@{NONE,CELLS,ALL@}
224 /FORMAT=@{TABLES,NOTABLES@}
225 @{LABELS,NOLABELS,NOVALLABS@}
230 /CELLS=@{COUNT,ROW,COLUMN,TOTAL,EXPECTED,RESIDUAL,SRESIDUAL,
231 ASRESIDUAL,ALL,NONE@}
232 /STATISTICS=@{CHISQ,PHI,CC,LAMBDA,UC,BTAU,CTAU,RISK,GAMMA,D,
233 KAPPA,ETA,CORR,ALL,NONE@}
236 /VARIABLES=var_list (low,high)@dots{}
239 The @cmd{CROSSTABS} procedure displays crosstabulation
240 tables requested by the user. It can calculate several statistics for
241 each cell in the crosstabulation tables. In addition, a number of
242 statistics can be calculated for each table itself.
244 The TABLES subcommand is used to specify the tables to be reported. Any
245 number of dimensions is permitted, and any number of variables per
246 dimension is allowed. The TABLES subcommand may be repeated as many
247 times as needed. This is the only required subcommand in @dfn{general
250 Occasionally, one may want to invoke a special mode called @dfn{integer
251 mode}. Normally, in general mode, PSPP automatically determines
252 what values occur in the data. In integer mode, the user specifies the
253 range of values that the data assumes. To invoke this mode, specify the
254 VARIABLES subcommand, giving a range of data values in parentheses for
255 each variable to be used on the TABLES subcommand. Data values inside
256 the range are truncated to the nearest integer, then assigned to that
257 value. If values occur outside this range, they are discarded. When it
258 is present, the VARIABLES subcommand must precede the TABLES
261 In general mode, numeric and string variables may be specified on
262 TABLES. Although long string variables are allowed, only their
263 initial short-string parts are used. In integer mode, only numeric
264 variables are allowed.
266 The MISSING subcommand determines the handling of user-missing values.
267 When set to TABLE, the default, missing values are dropped on a table by
268 table basis. When set to INCLUDE, user-missing values are included in
269 tables and statistics. When set to REPORT, which is allowed only in
270 integer mode, user-missing values are included in tables but marked with
271 an @samp{M} (for ``missing'') and excluded from statistical
274 Currently the WRITE subcommand is ignored.
276 The FORMAT subcommand controls the characteristics of the
277 crosstabulation tables to be displayed. It has a number of possible
282 TABLES, the default, causes crosstabulation tables to be output.
283 NOTABLES suppresses them.
286 LABELS, the default, allows variable labels and value labels to appear
287 in the output. NOLABELS suppresses them. NOVALLABS displays variable
288 labels but suppresses value labels.
291 PIVOT, the default, causes each TABLES subcommand to be displayed in a
292 pivot table format. NOPIVOT causes the old-style crosstabulation format
296 AVALUE, the default, causes values to be sorted in ascending order.
297 DVALUE asserts a descending sort order.
300 INDEX/NOINDEX is currently ignored.
303 BOX/NOBOX is currently ignored.
306 The CELLS subcommand controls the contents of each cell in the displayed
307 crosstabulation table. The possible settings are:
323 Standardized residual.
325 Adjusted standardized residual.
329 Suppress cells entirely.
332 @samp{/CELLS} without any settings specified requests COUNT, ROW,
333 COLUMN, and TOTAL. If CELLS is not specified at all then only COUNT
336 The STATISTICS subcommand selects statistics for computation:
340 Pearson chi-square, likelihood ratio, Fisher's exact test, continuity
341 correction, linear-by-linear association.
345 Contingency coefficient.
349 Uncertainty coefficient.
365 Spearman correlation, Pearson's r.
372 Selected statistics are only calculated when appropriate for the
373 statistic. Certain statistics require tables of a particular size, and
374 some statistics are calculated only in integer mode.
376 @samp{/STATISTICS} without any settings selects CHISQ. If the
377 STATISTICS subcommand is not given, no statistics are calculated.
379 @strong{Please note:} Currently the implementation of CROSSTABS has the
384 Pearson's R (but not Spearman) is off a little.
386 T values for Spearman's R and Pearson's R are wrong.
388 Significance of symmetric and directional measures is not calculated.
390 Asymmetric ASEs and T values for lambda are wrong.
392 ASE of Goodman and Kruskal's tau is not calculated.
394 ASE of symmetric somers' d is wrong.
396 Approximate T of uncertainty coefficient is wrong.
399 Fixes for any of these deficiencies would be welcomed.
401 @node T-TEST, ONEWAY, CROSSTABS, Statistics
402 @comment node-name, next, previous, up
408 /MISSING=@{ANALYSIS,LISTWISE@} @{EXCLUDE,INCLUDE@}
409 /CRITERIA=CIN(confidence)
417 (Independent Samples mode.)
418 GROUPS=var(value1 [, value2])
422 (Paired Samples mode.)
423 PAIRS=var_list [WITH var_list [(PAIRED)] ]
428 The @cmd{T-TEST} procedure outputs tables used in testing hypotheses about
430 It operates in one of three modes:
432 @item One Sample mode.
433 @item Independent Groups mode.
438 Each of these modes are described in more detail below.
439 There are two optional subcommands which are common to all modes.
441 The @cmd{/CRITERIA} subcommand tells PSPP the confidence interval used
442 in the tests. The default value is 0.95.
445 The @cmd{MISSING} subcommand determines the handling of missing
447 If INCLUDE is set, then user-missing values are included in the
448 calculations, but system-missing values are not.
449 If EXCLUDE is set, which is the default, user-missing
450 values are excluded as well as system-missing values.
453 If LISTWISE is set, then the entire case is excluded from analysis
454 whenever any variable specified in the @cmd{/VARIABLES}, @cmd{/PAIRS} or
455 @cmd{/GROUPS} subcommands contains a missing value.
456 If ANALYSIS is set, then missing values are excluded only in the analysis for
457 which they would be needed. This is the default.
461 * One Sample Mode:: Testing against a hypothesised mean
462 * Independent Samples Mode:: Testing two independent groups for equal mean
463 * Paired Samples Mode:: Testing two interdependent groups for equal mean
466 @node One Sample Mode, Independent Samples Mode, T-TEST, T-TEST
467 @subsection One Sample Mode
469 The @cmd{TESTVAL} subcommand invokes the One Sample mode.
470 This mode is used to test a population mean against a hypothesised
472 The value given to the @cmd{TESTVAL} subcommand is the value against
473 which you wish to test.
474 In this mode, you must also use the @cmd{/VARIABLES} subcommand to
475 tell PSPP which variables you wish to test.
477 @node Independent Samples Mode, Paired Samples Mode, One Sample Mode, T-TEST
478 @comment node-name, next, previous, up
479 @subsection Independent Samples Mode
481 The @cmd{GROUPS} subcommand invokes Independent Samples mode or
483 This mode is used to test whether two groups of values have the
484 same population mean.
485 In this mode, you must also use the @cmd{/VARIABLES} subcommand to
486 tell PSPP the dependent variables you wish to test.
488 The variable given in the @cmd{GROUPS} subcommand is the independent
489 variable which determines to which group the samples belong.
490 The values in parentheses are the specific values of the independent
491 variable for each group.
492 If the parentheses are omitted and no values are given, the default values
493 of 1.0 and 2.0 are assumed.
495 If the independent variable is numeric,
496 it is acceptable to specify only one value inside the parentheses.
497 If you do this, cases where the independent variable is
498 less than or equal to this value belong to the first group, and cases
499 greater than this value belong to the second group.
500 When using this form of the @cmd{GROUPS} subcommand, missing values in
501 the independent variable are excluded on a listwise basis, regardless
502 of whether @cmd{/MISSING=LISTWISE} was specified.
505 @node Paired Samples Mode, , Independent Samples Mode, T-TEST
506 @comment node-name, next, previous, up
507 @subsection Paired Samples Mode
509 The @cmd{PAIRS} subcommand introduces Paired Samples mode.
510 Use this mode when repeated measures have been taken from the same
512 If the the @code{WITH} keyword is omitted, then tables for all
513 combinations of variables given in the @cmd{PAIRS} subcommand are
515 If the @code{WITH} keyword is given, and the @code{(PAIRED)} keyword
516 is also given, then the number of variables preceding @code{WITH}
517 must be the same as the number following it.
518 In this case, tables for each respective pair of variables are
520 In the event that the @code{WITH} keyword is given, but the
521 @code{(PAIRED)} keyword is omitted, then tables for each combination
522 of variable preceding @code{WITH} against variable following
523 @code{WITH} are generated.
526 @node ONEWAY, , T-TEST, Statistics
527 @comment node-name, next, previous, up
531 @cindex analysis of variance
536 [/VARIABLES = ] var_list BY var
537 /MISSING=@{ANALYSIS,LISTWISE@} @{EXCLUDE,INCLUDE@}
538 /CONTRASTS= value1 [, value2] ... [,valueN]
539 /STATISTICS=@{DESCRIPTIVES,HOMOGENEITY@}
543 The @cmd{ONEWAY} procedure performs a one-way analysis of variance of
544 variables factored by a single independent variable.
545 It is used to compare the means of a population
546 divided into more than two groups.
548 The variables to be analysed should be given in the @code{VARIABLES}
550 The list of variables must be followed by the @code{BY} keyword and
551 the name of the independent (or factor) variable.
553 You can use the @code{STATISTICS} subcommand to tell PSPP to display
554 ancilliary information. The options accepted are:
557 Displays descriptive statistics about the groups factored by the independent
560 Displays the Levene test of Homogeneity of Variance for the
561 variables and their groups.
564 The @code{CONTRASTS} subcommand is used when you anticipate certain
565 differences between the groups.
566 The subcommand must be followed by a list of numerals which are the
567 coefficients of the groups to be tested.
568 The number of coefficients must correspond to the number of distinct
569 groups (or values of the independent variable).
570 If the total sum of the coefficients are not zero, then PSPP will
571 display a warning, but will proceed with the analysis.
572 The @code{CONTRASTS} subcommand may be given up to 10 times in order
573 to specify different contrast tests.