Physician Participants
Our goal was to achieve a stratified random sample of 20 physicians practicing in urban and rural settings from a sampling frame of 400 family physicians in London, Ontario, Canada, and the surrounding area. The family physician investigators telephoned a total of 44 physicians who were selected from the sampling frame using a random numbers table. This followed the recruitment process reported by Borgeil and colleagues.31 Physicians who agreed to participate in our study were mailed a letter of information, a consent form, and directions for the study protocol, including how to administer the WAST and a list of community resources for women who were abused.
Patient Participants
For patients, we followed the recommendations of DeVellis, who has outlined a sample size range with a minimum of 200 and a maximum of 1000 respondents to explore the factorial validity of a new measure.32 To ensure that sufficient variability would exist across responses, we aimed for a moderate sample size of approximately 300 subjects.
To be included in our study the women patients were required to be older than 18 years; attending for a periodic health examination, for prenatal care, or with acute symptoms of illness; English speaking; unaccompanied by another person; currently involved in an intimate relationship (married or common law); and they had to consider the attending physician their primary care physician.
Instrument Administration
The 20 participating physicians were asked to administer the WAST to 15 to 20 consecutive women patients who met the inclusion criteria and consented to participate in the study. At the conclusion of each patient visit the physicians were requested to complete the WAST comfort questionnaire and the prior knowledge questionnaire. When the data collection was completed they were asked to report their perceptions of the WAST.
Each woman was approached by the research assistant in one of the physician’s examining rooms before her visit with the family physician. The research assistant explained the study, provided the patient with a letter of information, and if she agreed to participate supplied a consent form for signature. During the patient recruitment process, the research assistant maintained a written log describing eligible and ineligible patients, reasons for refusal, and other pertinent data, such as the physician’s knowledge of whether a patient was in an abusive relationship. At the conclusion of the physician-patient encounter, the research assistant met with the patient in a private area and asked her to complete the ARI and the measure assessing her comfort with the WAST questions asked.
Data Analysis
To determine the reliability and validity of the WAST, we calculated Cronbach a and Pearson correlation coefficients for the WAST and the ARI. Differences in both the nominal-level demographic information of patients and the responses of physicians and patients to the study measures on the basis of selected variables (family practice certification status for physicians, positive versus negative screen for patients) were analyzed using cross-tabulations and chi-square calculations. Differences in interval and ratio level measures (including demographic information and scale totals) were analyzed with independent samples Student t tests. Analyses involving the length of time physicians had been in practice were conducted using a computed variable (1997 minus year of graduation), which was then recoded into the decade of graduation. Scoring of the WAST involved recoding the responses to reflect a higher score for higher reported frequency of experiences and then summing the WAST scores for individuals who answered all 8 items. ARI scores were calculated for respondents who had answered all 25 items using the procedure outlined by Yegidis.30
Results
Validity and Reliability of the WAST in the Family Practice Context Overall WAST and ARI scores were correlated (r=0.69, P=.01). The WAST was found to be a reliable measure in the family practice context, achieving a coefficient a of 0.75, indicating good internal consistency.
Physician Characteristics
To secure the 20 family physicians required for the study, we had to contact 44 physicians randomly selected from the sampling frame, yielding an acceptance rate of 45.5%. The final sample of physicians consisted of 7 women and 13 men. The average number of years since graduation was 22.9 (range=6-46 years). There were 8 physicians in rural practice and 12 from the city of London, Ontario. Fourteen were in a group practice arrangement, and 14 were certificants of the College of Family Physicians of Canada (CFPC). There were no significant differences between the physicians who agreed to participate and those who declined, on the basis of sex, certification status, years since graduation, practice type (solo vs group), and practice location (urban vs rural).