This chapter describes the methodology employed throughout
this
longitudinal project. Having already addressed this
project's
sampling technique and procedure of data collection in the
previous
chapter, a brief description of the Wave 2 response rates
will be
presented in the following section.
Data collection for Wave 2 began during the summer of 1991 and
was completed by the fall of 1992. Of the 1257 persons
interviewed
in Wave 1, 83 moved away from the city, eight were deemed
ineligible
(i.e., died or were institutionalized), 57 could not be
contacted and
121 refused to be reinterviewed. The number of completed
interviews
for Wave 2 was 988 and provided an overall response rate of
78.7
percent.
The following is a list and explanation of the instruments and
measures utilized throughout both waves of this
project. A battery
of demographic, alcohol abuse, personality and partner abuse
items
were administered in Wave 1 and then were readministered in
Wave 2.
Items designed to assess changes that might have occurred
during the
two year period between Wave 1 and Wave 2 as well as
questions that
might also elicit further information regarding the
circumstances
surrounding episodes of partner abuse were added to the
follow-up
interviews in Wave 2. These items will be noted below
where
applicable.
Demographic variables.
Questions were included to measure the
following demographic variables: (1) age, (2) gender, (3)
marital
status, (4) race, (5) religion, (6) employment status and (7)
income.
Items regarding changes with respect to marital status,
family size,
employment status, as well as income were added to the Wave 2
questionnaire (Appendix B. Part 1).
Alcohol abuse. Two
constructs were selected to assess the extent of
alcohol abuse by the respondents (i.e., alcohol consumption
and
alcohol dependence).
1) Alcohol consumption:
Alcohol consumption was measured by the Volume Variability
Index
(Cahalan & Cisin, 1986; Room, 1982). This
instrument contained nine
questions and measured the quantity-frequency (with an added
indicator for binge drinking) of wine, beer and liquor
consumption.
(Appendix B, Part 2). This measure is particularly
relevant because
of the association between alcohol consumption and the
perpetration
of violence consistently reported throughout the
literature. The
index selected for use in this research was the number of
ounces of
alcohol consumed per day.
2) Alcohol dependence:
An index was constructed to measure alcohol dependence
(Sommer,
Barnes & Murray, 1990). The Alcohol Dependence
Index was constructed
by assigning "0" and "1" values to scores
which respectively fell
below and above the scale cutpoints (based on those reported
in
clinical research on alcohol dependence). The values were
then summed
to produce a possible scale range of 0 to 3 whereby a score
of 0
indicated no indicators of alcoholism while a score of 3
reflected
being alcoholic on all indicators. It employed the
following
measures:
A) Michigan Alcoholism
Screening Test (SMAST) (Porkorny &
Miller, 1972) is a 13 item test
intended to screen individuals
in the general population and
one which has been widely used in
other studies (Appendix B, Part
3). The SMAST was designed to
produce a more
effective,shorter, self- administered and more
easily scored version of the
original MAST. In a study comparing
the two versions of the MAST,
reliability coefficient alphas
computed for the two comparison
group scores, yielded
coefficients only slightly
lower for the SMAST (Seltzer, Vinokur
& Rooijen, 1975). However,
validity coefficients on the other
hand were found to be slightly
higher for the same shortened
scale version. In light of
these findings, the authors concluded
that the SMAST is as effective
as the MAST in screening for
alcoholism.
B) The Alcohol Dependence
Data Schedule (SADD) (Raistrick,
Dunbar & Davidson, 1983) is
a 15 item instrument which has been
administered to both clinical
and non-clinical samples and has
been found to strongly
distinguish alcoholics from nonalcoholics
(Appendix B, Part 4). The
split- half reliability obtained by
Raistrick et al. (1983) using
the short form (i.e., the 15 item
scale used in this study) was
.87. Other research by Jorge and
Mazur (1985) employing this
shortened version obtained a split
half reliability of .88 when
used in an interview format and .82
when self- administered.
Results of the Wave 1 provided an
estimate of internal
consistency of .82 for females and .68 for
males.
3) A subscale of the NIMH
Diagnostic Interview Schedule Version
III, Revised (DIS) which
provides a number of indices of
alcoholism that follow the
diagnostic criteria of the Diagnostic
and Statistical Manual
(DSM-III) (American Psychiatric
Association, 1980) was
developed by Robins, Helzer, Croughan,
Williams and Spitzer (1979).
The subscale selected for use in
this research is the
"lifetime diagnosis of alcohol
dependence/abuse"
(Appendix B, Part 5).
Several instruments measuring the major dimensions of
personality
were selected for use in this research. They are as follows:
1) Eysenck Personality Questionnaire (EPQ-R) (1985):
The EPQ-R is a 100 item scale containing three personality
subscales:
Neuroticism (EPQN), Introversion-Extraversion (EPQE), and
Psychoticism (EPQP). The EPQ-R also contains a validity
scale, the
Lie Scale (EPQL) (Appendix B, Part 6). The Lie Scale may also
be
considered a measure of social conformity. While
Neuroticism and
Introversion-Extraversion are well established tests of
personality,
the Psychoticism dimension is newer and has been a source of
controversy. Earlier versions of this scale have been
criticized for
low reliabilities (i.e., Cronbach's Alpha = .74 for males and
.68 for
females) (Torrubia & Muntaner, 1987) and skewed
distributions
(Eysenck & Eysenck, 1975). The most recent version
(EPQ- R)
(Eysenck, Eysenck & Barrett, 1985) seems to have overcome
these
handicaps. Wave 1 data provided the following reliability
coefficient
alphas for the EPQ-R subscales: EPQN (males .85; females
.85), EPQE
(males .82; females .80), EPQP (males .60; females .61)
and EPQL
(males .83; females .82) (Sommer, 1990; Sommer et al., 1992).
2) MacAndrew Scale (MAC) (MacAndrew, 1965):
The MAC is a 51 item subscale of the Minnesota Multiphasic
Personality Inventory MMPI) (Appendix B, Part 7). It has been
successfully cross validated against samples similar to those
for
which it was originally developed (alcoholics versus
non-substance
abusing psychiatric patients) (MacAndrew, 1980). MacAndrew
(1980)
found that 85% of male alcoholics assessed by the MAC scale
were
classified as "secondary psychopaths" (i.e.,
neurotic extroverts)
according to Eysenck's model of personality. Whereas
results of Wave
1 data indicated that the MAC was a predictor of partner
abuse for
female respondents (Sommer et al., 1992), tests of
reliability
performed on these data provided low estimates of internal
consistency for both males (.43) (Sommer, 1990) and females
(.54)
(Sommer et al., 1992). These were likely due to the
multidimensional
nature of the scale. Earlywine, Fine and Martin (1990)
considered
the MAC a fallible indicator of underlying constructs. In
spite of
the MAC's low estimate of reliability, these authors
determined that
a confirmatory factor analysis demonstrated associations
between it
and personality measures. Other research by MacAndrew
(1980) showed
that the MAC is still considered an appropriate measure
because of
its widespread use and its demonstrated ability to
distinguish
between alcoholic and nonalcoholic populations.
3) Neuroticism Index:
In order to avoid the problems associated with
multicollinearity,
several highly correlated scales were combined to form a
Neuroticism
Index (Sommer, Barnes & Murray, 1990). A
conservative approach
toward selection of the measures based on the strength of
intercorrelations supported this procedure (Sommer et al.,
1992).
Support for combining these measures was also found in the
literature
on personality (Krisha, 1980; Rosenberg, 1979; Roy,
1977). The index
was constructed by averaging the means of the scales' z
scores.
Transformations were performed to ensure that all composite
measures
were scored in the same direction. The following
instruments were
included in this measure:
A) The Rosenberg Self-Esteem
Scale (Rosenberg, 1965) is a 10
item scale which has been found
to relate to alcoholism
(Beckman, 1978) as well as with
perpetrators of partner abuse
(Goldstein & Rosenbaum,
1985; Rouse, 1988; Barnes et al., 1990)
(Appendix B, Part 8). This
scale provided satisfactory estimates
of internal consistency on Wave
1 data for males (Alpha =.83)
(Sommer, 1990) and females
(Alpha =.86) (Sommer et al., 1992).
B) The Trait Anxiety Scale
(Spielberger, 1970), a widely used
measure of anxiety consists of
20 items (Appendix B, Part 9).
Since our earlier research on
abuse among male college students
found neuroticism to be a
significant predictor of abuse
(Barnes, Greenwood &
Sommer, 1991), this particular measure was
therefore thought to be
relevant in this present examination of
partner abuse. This measure
provided a satisfactory estimate of
internal consistency in Wave 1
for males (Alpha =.84) (Sommer,
1990) and females (Alpha =.88)
(Sommer et al., 1991).
C) The Baron Ego-Strength
Scale is another subscale of the MMPI
containing 67 items (Appendix
B, Part 10). It measures a general
factor of the capacity for
personalityintegration (Greene,
1980). According to
Greene (1980), persons who score high on
this measure are thought to
have secure self concepts and are
able to cope with
situationalstress. Low scorers on the other
hand, are more likely to
experience chronic, personality
problems. It was
suggested that those with less integrated
personalities might experience
lower levels of impulse control
and resort to more primitive
methods of coping such as violence
(Sommer, 1990). Analyses of
Wave 1 data provided somewhat low,
yet satisfactory estimates of
internal consistency for males
(.67) (Sommer, 1990) and
females (.70) (Sommer et al., 1992).
D) A fourth measure included
in the Neuroticism Index is the
EPQN
described above.
In order to address the issue of violence within the family of
origin, two questions were included in the Wave 2 interview
schedule
(Appendix B, Part 11).
Twelve items have been included in the Wave 2 interview
schedule to
assess the extent of life stress events experienced by
abusers and
their spouse/partners. The items selected are similar
to some of
those included in the Holmes and Rahe (1967) Life Stress
Events Scale
(Appendix B, Part 12).
In this project, the dependent variable, partner abuse was
measured
by an abridged version of Straus's (1979) Conflict Tactics
Scale
(CTS) (Form A). The scale measures the frequency with
which abusive
actions occur as well as the degree of its severity. An
individual
scoring low on the CTS is indicative of someone whose
experience with
partner abuse is both infrequent and less severe than one
scoring
high on the same measure. In this research, both the
prevalence
(i.e., abuse ever occurring during the course of a
relationship) and
incidence (i.e., reports of partner abuse incidents during
the past
year) of perpetrated partner abuse were assessed by this
measure. In
its original form, the CTS incorporates the following three
modes of
conflict resolution: (1) the use of rational discussion,
argument and
reasoning, (2) the use of verbal and nonverbal acts, and (3)
the use
of physical force against another person.
For the purposes of this
study, six items of the CTS measuring
"physical force" tactics were selected for
analyses. Items
associated with emotional abuse (i.e., rational discussion,
argument
and reasoning) were not considered relevant to this
investigation of
physical abuse and were therefore excluded. As well,
the most severe
"physical force" conflict tactics (i.e., beat up,
threatened with a
knife or gun, used a knife or gun) were also omitted because
of low
endorsement rates demonstrated in past research (i.e., 0% to
4%)
(Brinkerhoff & Lupri, 1988; Malone et al., 1989; Marshall
& Rose,
1990; Smith, 1987; Stets & Pirog-Good, 1989).
Furthermore, whereas many
studies have employed the full scale
in their analyses, portions of the scale have also been used
in other
research (Brinkerhoff & Lupri, 1988; Roscoe &
Benaske, 1985; Smith,
1987). In fact, the reliability of an abbreviated version
used in
Wave 1 of this project (Cronbach's Alpha =.79 for males and
Cronbach's Alpha =.94 for females) was found to show greater
internal
consistency than that of the entire scale used in our earlier
research on male perpetrated courtship violence (Cronbach's
Alpha
=.57) (Barnes, et al., 1991).
Various versions of the
scale have been used in face-to-face
interviews (Kennedy & Dutton, 1989; Schulman, 1981;
Smith, 1987;
Sommer, Barnes & Murray, 1990, 1991; Straus et al.,
1980), telephone
interviews (Straus & Gelles, 1986) and mail surveys
(Straus, 1979).
However as noted previously, the CTS is limited in its
ability to
elicit information on the following: (1) the circumstances
surrounding the violent episode occurred (i.e., who initiated
the
episode or did it occur in self defence), (2) whether the
consumption
of alcohol was involved prior to the violent episode, (3) the
consequences of violent episodes (i.e., physical injuries)
and (4)
whether episodes of abuse had been reported to the
police. The
revised version of the CTS employed in this study included
items
designed to overcome most of the noted limitations of
previous
research (Appendix C).
The data analyses conducted in this second phase of the
research
followed a similar format to that conducted during its first
phase
using SAS statistical packages (SAS Institute Inc.,
1986). Data from
both Waves 1 and 2 of the Winnipeg Health and Drinking Survey
(Barnes
& Murray, 1989) were used to test the theoretical issues
in this
research.
In light of the diminished
response rate reported earlier for
Wave 2, data analysis began with an investigation into the
effects of
sample attrition. Inspecting the data for possible
distortions
resulting from missing data is important because nonrandom
attrition
may pose a threat to internal and external validity (Stacy,
Newcomb &
Bentler, 1991). Determinations regarding the proportion
of partner
abusers from Wave 1 found among those who refused to
participate or
could not be contacted for Wave 2 data were made. In
addition,
possible differences between study dropouts and completers
with
respect to Wave 1 sample characteristics (i.e.,
socio-demographic and
personality factors, alcohol consumption and CTS scores) were
evaluated.
Assessing changes and
stability in prevalence rates of partner
abuse (i.e., has abuse "ever" occurred) as well as
in other
independent measures reported in Wave 1 and Wave 2 were
achieved by
way of frequency and correlational analyses. As was the
case in the
analysis of Wave 1 data, Pearson correlations were also
performed
within the Wave 2 data to assess the bivariate relationships
between
partner abuse.
The relationship between
alcohol consumption (Wave 2) and
partner abuse (Wave 2) were examined for linearity by
collapsing the
former variable into three levels (i.e., low, medium and high
alcohol
consumption) and then examining differences in the partner
abuse
score means. Linearity is established when the means of
the partner
abuse scores are found to increase across levels of alcohol
consumption.
The final phase of the data
analysis tested the major hypotheses
of this research using logistic regression analyses.
Given that
reported incidence rates for perpetrated partner abuse
(10-14%) fall
well below the 25 percent cutoff considered to be appropriate
for
inclusion as a dependent measure in a multiple regression
analyses
(Cleary & Angel, 1984), the selection of this approach
was considered
appropriate. The application of this procedure in
previous spousal
violence research (Bland & Orn, 1986; Kalmuss &
Seltzer, 1986;
Seltzer & Kalmuss, 1988) provided additional support for
use in this
research.
The logistic regression
approach has two distinct features; the
dependent variable is dichotomous, and the effects of the
independent
variables are presented as odds ratios. In order to
conform with the
former, this study's dependent measure, "current
perpetrated partner
abuse" (i.e., the number of times an individual
perpetrates partner
abuse during the past year) was collapsed into the following
two
levels: abuse as reported at any level of severity and/or
frequency
(coded as 1) and no abuse (coded as 2).
According to Halli and Rao
(1992), the odds ratio forms the
backbone of logistic regression. In this research,
logistic
regression analyses made it possible to establish the ratio
between
perpetrating and not perpetrating current partner abuse based
on a
number of underlying and situational factors. The
magnitude of each
predictor was also assessed through an examination of the
parameter
estimate in relation to the standard error. Finally,
the fit of the
model being tested (i.e., the degree to which the predictors
tested
were needed to model the dependent measure) was determined by
way of
chi-square analysis.
In spite of the
appropriateness of logistic regression in this
research, there are a number of limitations inherent in the
use of
this approach that are in need of consideration. For
example, a
problem associated with the severe skewness of the dependent
variable
is the potential instability of coefficient estimates
using this
statistical application (Seltzer & Kalmuss, 1988).
In order to
compensate for this problem, the following strategies put
forth by
Seltzer and Kalmuss (1988) were adopted in the logistic
regression
analyses conducted in this research:
1) Rather than including all
the main effects and interaction
effects in one model, the
interactions were estimated in two
separate models (i.e., one
examining interactions with stress
and the other examining
interactions with current alcohol
consumption).
2) Conservative standards
for the interpretation of results were
also employed. Thus,
"statistical significance was attributed
only when a coefficient was
twice the value of the standard
error" (p. 481, Seltzer
& Kalmuss, 1988).
The second issue relates to
a loss of sensitivity in the
dependent measure due to the transformations performed.
The
quantitative differences once present in the continuous
variable,
"current perpetrated partner abuse" were eliminated
when it was
collapsed into two levels. Thus, instead of assessing
the
perpetration of current partner abuse as ranging from low to
high
(with a possible range of 0 to 12), the transformed variable
can only
be interpreted as indicating either the presence or absence
of
current perpetrated partner abuse. To the extent that a
dichotomous
dependent measure is a necessary condition of logistic
regression,
its resulting lack of sensitivity must be viewed as an
unresolved
limitation in this approach, to be dealt with theoretically.
Next: Chapter 5
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