+@c PSPP - a program for statistical analysis.
+@c Copyright (C) 2017 Free Software Foundation, Inc.
+@c Permission is granted to copy, distribute and/or modify this document
+@c under the terms of the GNU Free Documentation License, Version 1.3
+@c or any later version published by the Free Software Foundation;
+@c with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+@c A copy of the license is included in the section entitled "GNU
+@c Free Documentation License".
+@c
@alias prompt = sansserif
@include tut.texi
* Reading data from a pre-prepared PSPP file::
* Saving data to a PSPP file.::
* Reading data from other sources::
+* Exiting PSPP::
@end menu
@node Defining Variables
It should show the following output:
@example
@group
-Case# forename height
------ ------------ --------
- 1 Ahmed 188.00
- 2 Bertram 167.00
- 3 Catherine 134.23
- 4 David 109.10
+ Data List
++-----------+---------+------+
+|Case Number| forename|height|
++-----------+---------+------+
+|1 |Ahmed |188.00|
+|2 |Bertram |167.00|
+|3 |Catherine|134.23|
+|4 |David |109.10|
++-----------+---------+------+
@end group
@end example
@noindent
In these instances you should
use the @cmd{GET DATA} command (@pxref{GET DATA}).
+@node Exiting PSPP
+@subsection Exiting PSPP
+
+Use the @cmd{FINISH} command to exit PSPP:
+@example
+@prompt{PSPP>} finish.
+@end example
@node Data Screening and Transformation
@section Data Screening and Transformation
Output:
@example
-DESCRIPTIVES. Valid cases = 40; cases with missing value(s) = 0.
-+--------#--+-------+-------+-------+-------+
-|Variable# N| Mean |Std Dev|Minimum|Maximum|
-#========#==#=======#=======#=======#=======#
-|sex #40| .45| .50| .00| 1.00|
-|height #40|1677.12| 262.87| 179.00|1903.00|
-|weight #40| 72.12| 26.70| -55.60| 92.07|
-+--------#--+-------+-------+-------+-------+
+ Descriptive Statistics
++---------------------+--+-------+-------+-------+-------+
+| | N| Mean |Std Dev|Minimum|Maximum|
++---------------------+--+-------+-------+-------+-------+
+|Sex of subject |40| .45| .50|Male |Female |
+|Weight in kilograms |40| 72.12| 26.70| -55.6| 92.1|
+|Height in millimeters|40|1677.12| 262.87| 179| 1903|
+|Valid N (listwise) |40| | | | |
+|Missing N (listwise) | 0| | | | |
++---------------------+--+-------+-------+-------+-------+
@end example
@end cartouche
@caption{Using the @cmd{DESCRIPTIVES} command to display simple
We can examine the data in more detail with the @cmd{EXAMINE}
command (@pxref{EXAMINE}):
-In @ref{examine} you can see that the lowest value of @var{height} is
+In @ref{ex1} you can see that the lowest value of @var{height} is
179 (which we suspect to be erroneous), but the second lowest is 1598
which
we know from the @cmd{DESCRIPTIVES} command
This suggests that the two extreme values are outliers and probably
represent data entry errors.
-@float Example, examine
+@float Example, ex1
@cartouche
[@dots{} continue from @ref{descriptives}]
@example
Output:
@example
-#===============================#===========#=======#
-# #Case Number| Value #
-#===============================#===========#=======#
-#Height in millimetres Highest 1# 14|1903.00#
-# 2# 15|1884.00#
-# 3# 12|1801.65#
-# ----------#-----------+-------#
-# Lowest 1# 30| 179.00#
-# 2# 31|1598.00#
-# 3# 28|1601.00#
-# ----------#-----------+-------#
-#Weight in kilograms Highest 1# 13| 92.07#
-# 2# 5| 92.07#
-# 3# 17| 91.74#
-# ----------#-----------+-------#
-# Lowest 1# 38| -55.60#
-# 2# 39| 54.48#
-# 3# 33| 55.45#
-#===============================#===========#=======#
+ Extreme Values
++-------------------------------+-----------+-----+
+| |Case Number|Value|
++-------------------------------+-----------+-----+
+|Height in millimeters Highest 1| 14| 1903|
+| 2| 15| 1884|
+| 3| 12| 1802|
+| Lowest 1| 30| 179|
+| 2| 31| 1598|
+| 3| 28| 1601|
++-------------------------------+-----------+-----+
+|Weight in kilograms Highest 1| 13| 92.1|
+| 2| 5| 92.1|
+| 3| 17| 91.7|
+| Lowest 1| 38|-55.6|
+| 2| 39| 54.5|
+| 3| 33| 55.4|
++-------------------------------+-----------+-----+
@end example
@end cartouche
@caption{Using the @cmd{EXAMINE} command to see the extremities of the data
For detailed information about the @cmd{RECODE} command @pxref{RECODE}.
If you now re-run the @cmd{DESCRIPTIVES} or @cmd{EXAMINE} commands in
-@ref{descriptives} and @ref{examine} you
+@ref{descriptives} and @ref{ex1} you
will see a data summary with more plausible parameters.
You will also notice that the data summaries indicate the two missing values.
reliability.
This gives the statistician some confidence that the questionnaires have been
completed thoughtfully.
-If you examine the labels of variables @var{v1}, @var{v3} and @var{v5},
+If you examine the labels of variables @var{v1}, @var{v3} and @var{v4},
you will notice that they ask very similar questions.
One would therefore expect the values of these variables (after recoding)
to closely follow one another, and we can test that with the @cmd{RELIABILITY}
command (@pxref{RELIABILITY}).
@ref{reliability} shows a @pspp{} session where the user (after recoding
negatively scaled variables) requests reliability statistics for
-@var{v1}, @var{v3} and @var{v5}.
+@var{v1}, @var{v3} and @var{v4}.
@float Example, reliability
@cartouche
@prompt{PSPP>} * recode negatively worded questions.
@prompt{PSPP>} compute v3 = 6 - v3.
@prompt{PSPP>} compute v5 = 6 - v5.
-@prompt{PSPP>} reliability v1, v3, v5.
+@prompt{PSPP>} reliability v1, v3, v4.
@end example
Output (dictionary information omitted for clarity):
@example
-1.1 RELIABILITY. Case Processing Summary
-#==============#==#======#
-# # N| % #
-#==============#==#======#
-#Cases Valid #17|100.00#
-# Excluded# 0| .00#
-# Total #17|100.00#
-#==============#==#======#
-
-1.2 RELIABILITY. Reliability Statistics
-#================#==========#
-#Cronbach's Alpha#N of Items#
-#================#==========#
-# .86# 3#
-#================#==========#
+Scale: ANY
+
+Case Processing Summary
++--------+--+-------+
+|Cases | N|Percent|
++--------+--+-------+
+|Valid |17| 100.0%|
+|Excluded| 0| .0%|
+|Total |17| 100.0%|
++--------+--+-------+
+
+ Reliability Statistics
++----------------+----------+
+|Cronbach's Alpha|N of Items|
++----------------+----------+
+| .81| 3|
++----------------+----------+
@end example
@end cartouche
@caption{Recoding negatively scaled variables, and testing for
reliability with the @cmd{RELIABILITY} command. The Cronbach Alpha
coefficient suggests a high degree of reliability among variables
-@var{v1}, @var{v2} and @var{v5}.}
+@var{v1}, @var{v3} and @var{v4}.}
@end float
As a rule of thumb, many statisticians consider a value of Cronbach's Alpha of
0.7 or higher to indicate reliable data.
-Here, the value is 0.86 so the data and the recoding that we performed
+Here, the value is 0.81 so the data and the recoding that we performed
are vindicated.
Output:
@example
-1.2 EXAMINE. Descriptives
-#====================================================#=========#==========#
-# #Statistic|Std. Error#
-#====================================================#=========#==========#
-#mtbf Mean # 8.32 | 1.62 #
-# 95% Confidence Interval for Mean Lower Bound# 4.85 | #
-# Upper Bound# 11.79 | #
-# 5% Trimmed Mean # 7.69 | #
-# Median # 8.12 | #
-# Variance # 39.21 | #
-# Std. Deviation # 6.26 | #
-# Minimum # 1.63 | #
-# Maximum # 26.47 | #
-# Range # 24.84 | #
-# Interquartile Range # 5.83 | #
-# Skewness # 1.85 | .58 #
-# Kurtosis # 4.49 | 1.12 #
-#====================================================#=========#==========#
-
-2.2 EXAMINE. Descriptives
-#====================================================#=========#==========#
-# #Statistic|Std. Error#
-#====================================================#=========#==========#
-#mtbf_ln Mean # 1.88 | .19 #
-# 95% Confidence Interval for Mean Lower Bound# 1.47 | #
-# Upper Bound# 2.29 | #
-# 5% Trimmed Mean # 1.88 | #
-# Median # 2.09 | #
-# Variance # .54 | #
-# Std. Deviation # .74 | #
-# Minimum # .49 | #
-# Maximum # 3.28 | #
-# Range # 2.79 | #
-# Interquartile Range # .92 | #
-# Skewness # -.16 | .58 #
-# Kurtosis # -.09 | 1.12 #
-#====================================================#=========#==========#
+ Case Processing Summary
++-----------------------------------+-------------------------------+
+| | Cases |
+| +----------+---------+----------+
+| | Valid | Missing | Total |
+| | N|Percent|N|Percent| N|Percent|
++-----------------------------------+--+-------+-+-------+--+-------+
+|Mean time between failures (months)|15| 100.0%|0| .0%|15| 100.0%|
++-----------------------------------+--+-------+-+-------+--+-------+
+
+ Descriptives
++----------------------------------------------------------+---------+--------+
+| | | Std. |
+| |Statistic| Error |
++----------------------------------------------------------+---------+--------+
+|Mean time between Mean | 8.32| 1.62|
+|failures (months) 95% Confidence Interval Lower | 4.85| |
+| for Mean Bound | | |
+| Upper | 11.79| |
+| Bound | | |
+| 5% Trimmed Mean | 7.69| |
+| Median | 8.12| |
+| Variance | 39.21| |
+| Std. Deviation | 6.26| |
+| Minimum | 1.63| |
+| Maximum | 26.47| |
+| Range | 24.84| |
+| Interquartile Range | 5.83| |
+| Skewness | 1.85| .58|
+| Kurtosis | 4.49| 1.12|
++----------------------------------------------------------+---------+--------+
+
+ Case Processing Summary
++-------+-------------------------------+
+| | Cases |
+| +----------+---------+----------+
+| | Valid | Missing | Total |
+| | N|Percent|N|Percent| N|Percent|
++-------+--+-------+-+-------+--+-------+
+|mtbf_ln|15| 100.0%|0| .0%|15| 100.0%|
++-------+--+-------+-+-------+--+-------+
+
+ Descriptives
++----------------------------------------------------+---------+----------+
+| |Statistic|Std. Error|
++----------------------------------------------------+---------+----------+
+|mtbf_ln Mean | 1.88| .19|
+| 95% Confidence Interval for Mean Lower Bound| 1.47| |
+| Upper Bound| 2.29| |
+| 5% Trimmed Mean | 1.88| |
+| Median | 2.09| |
+| Variance | .54| |
+| Std. Deviation | .74| |
+| Minimum | .49| |
+| Maximum | 3.28| |
+| Range | 2.79| |
+| Interquartile Range | .92| |
+| Skewness | -.16| .58|
+| Kurtosis | -.09| 1.12|
++----------------------------------------------------+---------+----------+
@end example
@end cartouche
@caption{Testing for normality using the @cmd{EXAMINE} command and applying
@end example
Output:
@example
-1.1 T-TEST. Group Statistics
-#==================#==#=======#==============#========#
-# sex | N| Mean |Std. Deviation|SE. Mean#
-#==================#==#=======#==============#========#
-#height Male |22|1796.49| 49.71| 10.60#
-# Female|17|1610.77| 25.43| 6.17#
-#temperature Male |22| 36.68| 1.95| .42#
-# Female|18| 37.43| 1.61| .38#
-#==================#==#=======#==============#========#
-1.2 T-TEST. Independent Samples Test
-#===========================#=========#=============================== =#
-# # Levene's| t-test for Equality of Means #
-# #----+----+------+-----+------+---------+- -#
-# # | | | | | | #
-# # | | | |Sig. 2| | #
-# # F |Sig.| t | df |tailed|Mean Diff| #
-#===========================#====#====#======#=====#======#=========#= =#
-#height Equal variances# .97| .33| 14.02|37.00| .00| 185.72| ... #
-# Unequal variances# | | 15.15|32.71| .00| 185.72| ... #
-#temperature Equal variances# .31| .58| -1.31|38.00| .20| -.75| ... #
-# Unequal variances# | | -1.33|37.99| .19| -.75| ... #
-#===========================#====#====#======#=====#======#=========#= =#
+ Group Statistics
++-------------------------------------------+--+-------+-------------+--------+
+| | | | Std. | S.E. |
+| Group | N| Mean | Deviation | Mean |
++-------------------------------------------+--+-------+-------------+--------+
+|Height in millimeters Male |22|1796.49| 49.71| 10.60|
+| Female|17|1610.77| 25.43| 6.17|
++-------------------------------------------+--+-------+-------------+--------+
+|Internal body temperature in degrees Male |22| 36.68| 1.95| .42|
+|Celcius Female|18| 37.43| 1.61| .38|
++-------------------------------------------+--+-------+-------------+--------+
+
+ Independent Samples Test
++---------------------+-----------------------------------------------------
+| | Levene's
+| | Test for
+| | Equality
+| | of
+| | Variances T-Test for Equality of Means
+| +----+-----+-----+-----+-------+----------+----------+
+| | | | | | | | |
+| | | | | | | | |
+| | | | | | | | |
+| | | | | | | | |
+| | | | | | Sig. | | |
+| | | | | | (2- | Mean |Std. Error|
+| | F | Sig.| t | df |tailed)|Difference|Difference|
++---------------------+----+-----+-----+-----+-------+----------+----------+
+|Height in Equal | .97| .331|14.02|37.00| .000| 185.72| 13.24|
+|millimeters variances| | | | | | | |
+| assumed | | | | | | | |
+| Equal | | |15.15|32.71| .000| 185.72| 12.26|
+| variances| | | | | | | |
+| not | | | | | | | |
+| assumed | | | | | | | |
++---------------------+----+-----+-----+-----+-------+----------+----------+
+|Internal Equal | .31| .581|-1.31|38.00| .198| -.75| .57|
+|body variances| | | | | | | |
+|temperature assumed | | | | | | | |
+|in degrees Equal | | |-1.33|37.99| .190| -.75| .56|
+|Celcius variances| | | | | | | |
+| not | | | | | | | |
+| assumed | | | | | | | |
++---------------------+----+-----+-----+-----+-------+----------+----------+
+
++---------------------+-------------+
+| | |
+| | |
+| | |
+| | |
+| | |
+| +-------------+
+| | 95% |
+| | Confidence |
+| | Interval of |
+| | the |
+| | Difference |
+| +------+------+
+| | Lower| Upper|
++---------------------+------+------+
+|Height in Equal |158.88|212.55|
+|millimeters variances| | |
+| assumed | | |
+| Equal |160.76|210.67|
+| variances| | |
+| not | | |
+| assumed | | |
++---------------------+------+------+
+|Internal Equal | -1.91| .41|
+|body variances| | |
+|temperature assumed | | |
+|in degrees Equal | -1.89| .39|
+|Celcius variances| | |
+| not | | |
+| assumed | | |
++---------------------+------+------+
@end example
@end cartouche
@caption{The @cmd{T-TEST} command tests for differences of means.
@prompt{PSPP>} regression /variables = mtbf duty_cycle /dependent = mttr.
@prompt{PSPP>} regression /variables = mtbf /dependent = mttr.
@end example
-Output:
+Output (excerpts):
@example
-1.3(1) REGRESSION. Coefficients
-#=============================================#====#==========#====#=====#
-# # B |Std. Error|Beta| t #
-#========#====================================#====#==========#====#=====#
-# |(Constant) #9.81| 1.50| .00| 6.54#
-# |Mean time between failures (months) #3.10| .10| .99|32.43#
-# |Ratio of working to non-working time#1.09| 1.78| .02| .61#
-# | # | | | #
-#========#====================================#====#==========#====#=====#
-
-1.3(2) REGRESSION. Coefficients
-#=============================================#============#
-# #Significance#
-#========#====================================#============#
-# |(Constant) # .10#
-# |Mean time between failures (months) # .00#
-# |Ratio of working to non-working time# .55#
-# | # #
-#========#====================================#============#
-2.3(1) REGRESSION. Coefficients
-#============================================#=====#==========#====#=====#
-# # B |Std. Error|Beta| t #
-#========#===================================#=====#==========#====#=====#
-# |(Constant) #10.50| .96| .00|10.96#
-# |Mean time between failures (months)# 3.11| .09| .99|33.39#
-# | # | | | #
-#========#===================================#=====#==========#====#=====#
-
-2.3(2) REGRESSION. Coefficients
-#============================================#============#
-# #Significance#
-#========#===================================#============#
-# |(Constant) # .06#
-# |Mean time between failures (months)# .00#
-# | # #
-#========#===================================#============#
+ Coefficients (Mean time to repair (hours) )
++------------------------+-----------------------------------------+-----+----+
+| | Unstandardized Standardized | | |
+| | Coefficients Coefficients | | |
+| +---------+-----------+-------------------+ | |
+| | B | Std. Error| Beta | t |Sig.|
++------------------------+---------+-----------+-------------------+-----+----+
+|(Constant) | 9.81| 1.50| .00| 6.54|.000|
+|Mean time between | 3.10| .10| .99|32.43|.000|
+|failures (months) | | | | | |
+|Ratio of working to non-| 1.09| 1.78| .02| .61|.552|
+|working time | | | | | |
++------------------------+---------+-----------+-------------------+-----+----+
+
+ Coefficients (Mean time to repair (hours) )
++-----------------------+------------------------------------------+-----+----+
+| | Unstandardized Standardized | | |
+| | Coefficients Coefficients | | |
+| +---------+------------+-------------------+ | |
+| | B | Std. Error | Beta | t |Sig.|
++-----------------------+---------+------------+-------------------+-----+----+
+|(Constant) | 10.50| .96| .00|10.96|.000|
+|Mean time between | 3.11| .09| .99|33.39|.000|
+|failures (months) | | | | | |
++-----------------------+---------+------------+-------------------+-----+----+
@end example
@end cartouche
@caption{Linear regression analysis to find a predictor for
projects / pspp / blobdiff