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What it Does
ZumaStat offers an add-on for SPSS that
simplifies many tasks for you. ZumaStat is compatible with versions 7.0 or
higher of SPSS. It integrates seamlessly with any version of SPSS
greater than 7.0. It is compatible with versions of SPSS 12 or higher,
which permit variable names longer than 8 characters. Here is what ZumaStat's SPSS interface can do for you:
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Create Dummy Variables: Ever want
to create dummy variables for a categorical variable? Doing so through the SPSS Transform menu is straightforward but inefficient. ZumaStat creates
dummy variables for you with just a click
of a few buttons on a single screen. ZumaStat will do dummy coding or
effect coding.
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Growth Curve Data:
Many growth curve programs that import SPSS data require that the repeated
measure data be structured in rows rather than columns. ZumaStat will
convert your SPSS data file to such a format with ease and will add dummy
variables for respondents with just a few mouse clicks. The ZumaStat
programs make it easy to structure data files that are compatible with the
popular HLM computer program. ZumaStat also includes a utility that passes
data to Excel and then plots growth curves for each individual case in a
file. This utility is useful for seeing trends in growth curves for
individuals considered separately rather than aggregated.
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Mean Center a Variable:
For many regression analyses, it is useful to center a predictor variable
about its mean. ZumaStat allows you to do so with one or two mouse clicks.
You can also easily "center" a variable one standard deviation above or
below its mean value with one simple click.
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Mean Center a Variable Within Strata.
ZumaStat will also mean center variables within strata or as a function of a
break variable. For example, if the break variable is gender and it has two
values, then the mean for males is calculated and the mean for females is
calculated. The male mean is subtracted from all scores of males and the
female mean is subtracted from all scores of females.
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Product Terms:
Interaction analysis in regression requires product terms. ZumaStat offers
two utilities that greatly simplify the calculation of product terms. This
is really quick and easy to do, whereas it is a cumbersome process in SPSS.
For example, in one routine, you specify the variables you want to focus on,
and ZumaStat automatically calculates all possible product terms between
them and inserts variable labels to identify them.
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Reformat a Correlation Matrix:
Pivot tables are nice, but did you ever try to look at a large correlation
matrix and examine the correlations on the right side of the matrix. This
is a great headache in SPSS. ZumaStat will reformat a correlation matrix
for you so you can see all the results on a single screen on your monitor.
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Missing Data Dummy Variables:
When you have missing data, you often want to determine if the data are
missing at random or if there is bias in the missing data pattern. One way
of approaching this for a given variable, X, is to create a dummy variable
for X, where a score of 1 is assigned to cases with missing data and a score
of 0 is assigned to cases with non-missing data. This dummy variable can
then be correlated with other variables to determine if it is associated
with them. For example, if the missing data dummy variable is significantly
correlated with gender, then this suggests that the data are not missing at
random and that males are more or less likely to have missing data than
females. ZumaStat creates missing data dummy variables for you for as many
as 400 variables all with a few mouse clicks.
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Change User Missing to System Missing Values:
ZumaStat allows you with the click of one button to change user missing
values to system missing values for all variables in a data set.
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Drop Variables from an Active Data File:
ZumaStat allows you to easily drop variables from an active data file, using
simple point and click.
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Reorder Variables in an Active Data File:
ZumaStat allows you to easily reorder variables in an active data
file, using simple point and click.
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Remove Scientific Notation and Change Decimals in a
Pivot Table. With the click of a button, you can change the
number of decimals displayed in a Pivot Table and remove scientific
notation. ZumaStat does this much more quickly and efficiently than SPSS.
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Copy Value Labels. ZumaStat has a
routine that allows you to easily copy the value labels from one variable to
one or more other variables.
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Weighted Combinations of Variables:
This routine creates a new variable that is a weighted sum of other
variables in your data file. For example, if you target three
variables, V1, V2 and V3, and specify weights for each (using ZumaStat
interface), then ZumaStat creates a new variable (NV) that equalsV = w1*V1 +
w2*V2 + w3*V3, where w is a weight. If you have three variables and
you want the new variable to be the sum of the three, set w1=1, w2=1 and
w3=1. If you want the new variable to be the average of the three, set
w1=.333, w2=.333 and w3=.333. If you want the new variable to be the average
of the first two variables minus the third variable, set w1=.5, w2=.5 and
w3=-1. ZumaSta provides shortcut check boxes to generate a new
variable that is the mean or sum of a set of variables.
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Variable List:
If you have a file with many variables in it, you might have SPSS set so
that it shows you the variables in a variable list in the same order that
they occur in the data file. Suppose that you want to locate a
certain variable whose name you know, but you can not remember where in the
file it occurs. You could change SPSS so that it shows the variables in
alphabetical order, but this is laborious.
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The program 'Variable List' in ZumaStat
gives you a list of the variables in the data file that can be shown in
either alphabetical order or in the order they appear in the file, with or
without labels and you can move between these formats with a simple click of
the button. If you click on the variable in the list, ZumaStat will
tell you the variable's ordinal position in the file listing as well as the
name of the variables that precedes it and that are just after it. This
will make it easier for you to find the variable in the file listing. The
Variable List window always remains “on top" so that you can see it as you
work with SPSS.
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Eliminate Cases with Missing Data
from the Data File: Some programs that interface
with SPSS require that there be no missing data in a file (e.g., HLM, some
applications of AMOS). Although you can easily invoke listwise deletion of
missing data in any of SPSS's statistical routines, it is quite another
matter to eliminate cases from a data file based on missing data across
multiple variables. ZumaStat offers a utility that does so with a few mouse
clicks.
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Cross-Validation:
ZumaStat has several utilities that facilitate cross-validation analyses.
One utility uses point and click to randomly divide a sample in half and
create two separate data files with each half in them. Another utility
randomly divides cases into any number of groups you specify and then
creates a break variable identifying the different groups for use of the
Split File capability of SPSS.
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Date Variables:
ZumaStat provides you a simple pont and click method for working with date
variables. Specify two date variables and this utility creates a new
variable that is the number of days, months or years between the two dates.
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Excel Graphics:
ZumaStat interfaces SPSS and Excel and creates graphs of SPSS data using the
Excel graphics programs. An advantage of this is that Excel offers a wider
range of graph types that can be easily cut and pasted into other
applications. If you work with Word, Powerpoint and other Microsoft
products, there are advantages of pasting graphs from Excel due to
compatibility and flexible editing issues. ZumaStat plots SPSS data in Excel for
one way frequencies, two way contingency tables, means for single factor
designs, means for two factor designs, scatter plots, and graphs to
explore growth curves at the level of single respondents, all with just a
few mouse clicks.
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Smoothed Scatterplots: Ever form a scatter plot between two
variables that are correlated 0.30 or so and have a blob of points appear
before you? Smoothed scatterplots can be revealing in such instances.
ZumaStat offers the option of a smoothed scatterplot using Excel. Smoothed
scatterplots are not available in SPSS.
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Creating Difference Scores:
ZumaStat describes shortcuts you can use to effectively analyze data in
repeated measure factorial designs. One of these relies on the
analysis of difference scores. ZumaStat offers a routine that quickly
and easily calculates all possible difference scores among a set of
variables.
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Save Filtered Cases:
If you want to save cases to a new SPSS file but apply a filter so that only
a subset of the cases are saved, you must again get into pasting and editing
syntax. ZumaStat greatly simplifies this process and circumvents working
with syntax.
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Web Page Links:
ZumaStat includes some useful links to web pages focused on statistics and
SPSS support groups.
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Add or
Subtract Constants to Many Variables: To add or
subtract a constant from a variable, you have to go through about a half a
dozen clicks for each variable as you navigate the SPSS Transform menu.
With the ZumaStat utility, you can easily accomplish this transformation for
up to 10 variables, all from a single screen and with relative ease. This
can particularly be useful for "centering" variables about different values
for purposes of interaction analysis.
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Exchange Values:
If you rely on the parameter estimates of SPSS's GLM program to isolate
single degree of freedom contrasts, then you know that you often have to
change the reference group in order to isolate the coefficient that is of
theoretical interest to you. SPSS allows you to change the reference group
from being the first to the last group, but this often does not do the
trick. Rather, you must recode and exchange values (e.g., recode scores on
a factor so that those individuals with a 2 on the factor now have a score
of 1 and vice versa). You can do this using the recode routine in SPSS, but
ZumaStat greatly simplifies the process for you.
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Exporting Data:
Exporting a data file to other formats (e.g., ascii, Excel)
is straightforward in SPSS but not if you only want to export a subset of
the variables in the data set. To accomplish this you must paste syntax and
modify the syntax while keeping variable names in mind. ZumaStat allows you
to export subsets of variables with a few mouse clicks. Exporting is truly
simple.
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Grouping Scores on a Variable:
Suppose you want to recode scores on a variable so that individuals with
values between 1 and 5 are in one group, those with scores of 6 to 10 are in
another group, and so on. ZumaStat makes this operation simple,
circumventing the more complicated recode and transformation utilities of SPSS.
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Reverse Score Variables:
ZumaStat makes it very easy to reverse score a variable (e.g., change the
scoring from 1 to 5 to 5 to 1).
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Rename
Variables:
Renaming a variable is straightforward but cumbersome in SPSS. ZumaStat makes it easy to rename
many variables with just a few mouse clicks.
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Reduce Factorial Design to a One Factor Design:
ZumaStat uses simple point and click to reduce a factorial design to a
one-way factor. For example, if you have a 3X2 design, this utility will
turn it into a one-way design with six groups. A new variable is created
with the numbers 1 to 6, each identifying group membership based on the
original six groups. This utility is useful so that you can use the SPSS
program 'One Way ANOVA' to apply contrast coefficients that involve special
contrasts in a 'factorial' design. The logic is developed in ZumaStat's
extensive Users Manual.
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Matrix Operations: Using matrix
manipulations in SPSS requires knowledge of the syntax language. ZumaStat
uses the SPSS matrix language to make it easy to perform basic matrix
operations through point and click. The operations include absolute value,
Cholesky decomposition, determinant, eigenvalues, exponentiation,
generalized inverse, inverse, rank, scalar multiply, square root, trace and
transpose. ZumaStat also uses SPSS matrix language to make it easy for you
to add, subtract, multiply or divide two matrices, as well as to compute
Kronecker products, element-wise multiplication and element-wise division.
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Create Simulation Data:
ZumaStat has a complete package for generating data for simulations. It allows you to create a set of random variables for a user selected
number of cases such that the variables come from either a normal
distribution, a chi square distribution, a log normal distribution, a uniform distribution
or a mixed normal distribution. This is
useful for conducting simulations. You can also create data for
variables with a specified population correlation matrix and format data in such a
way that simulation studies are relatively easy to do.
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Create Input for LISREL:
Although LISREL now imports SPSS data files, there are times when it will be
more convenient to output a correlation matrix with means and standard
deviations in ascii files for input into LISREL. ZumaStat offers this
possibility with a few mouse clicks as well as the ability to output ascii
raw data in free field format that is compatible with LISREL.
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Analysis of Change:
ZumaStat offers a suite of programs that provides
useful perspectives on the analysis of change between two time points.
Within Z Plus, it has a utility that will calculate six types of change
scores, (1) raw change, (2) the reliable change index (RCI) that is popular
in clinical psychology, (3) an ordinal version of the RCI, (4) a
residualized change score, (5) a backward residualized change score, and (6)
the Lord-McNemar true change score. ZumaStat interfaces with Excel to
generate Galton squeeze diagrams, a useful graphic for visualizing
regression to the mean. It also offers Pair-Link plots to better see
individual change. ZumaStat offers utilities to determine the reliability of
change scores from the reliability of its component parts, inherent
correlations between pretest and change scores by virtue of part-whole
dynamics, and the biasing effects of regression to the mean in intervention
studies where there are pre-existing differences on the pretest in the
treatment and control groups.
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State-of-the-Art Missing Data Methods:
It is now commonly recognized that the traditional
strategies of pairwise and listwise deletion of missing data can be
suboptimal in many situations. An alternative approach based on Bayesian
and maximum likelihood imputations has evolved which is quite flexible and
has many desirable properties. However, the few available software programs
that implement these approaches are difficult to use. There is a free
computer program developed by researchers at Harvard that is reasonably
simple to use and that represents state-of-the-art imputation analysis. It
is called Amelia. ZumaStat has utilities to assist you in acquiring and
installing Amelia then interfacing it with SPSS. Amelia can be applied to
missing data scenarios in analysis of variance, OLS regression, logistic
regression, structural equation modeling and a wide range of other
statistical models. It can accommodate continuous, ordinal or nominal level
missing data. ZumaStat makes using Amelia much easier within the SPSS
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Simple SPSS Integration:
ZumaStat integrates conveniently with SPSS, becoming part of the SPSS menu
bar so that you may easily and conveniently access it as you work in SPSS.
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