WINNIPEG HEALTH AND DRINKING SURVEY - WAVE 2
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.
Independent Variables and Measures
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
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).
Conflict Tactics Scale.
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,
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
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
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
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).
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 Part 1