PubMed Health⌕ Search

Biomedical subjects

P A Cohen

Publications and source records attributed to P A Cohen.

At least 19 recordsLinked to original sources
PubMed1992

Gatekeeping.

Explore the source record for details and available documents.

Interprofessional Relations↗
PubMed1992

Oral contraceptive use and cardiovascular disease: is the relationship real or due to study bias?

BACKGROUND: Epidemiologic studies link oral contraceptive use with several cardiovascular events, but the literature is difficult to summarize, and potential biases remain poorly addressed. This study uses meta-analysis to summarize study results and to analyze the influence of study characteristics, including susceptibility to bias, on study outcome. METHODS: Forty-seven case-control and cohort studies of oral contraceptives and four cardiovascular events were coded for relative risk (RR) and study characteristics, including adherence to 14 bias-control standards. Key RRs were pooled to summarize findings for each disease type. Univariate determinants of the magnitude of the relative risks were identified, and partial correlation analysis was performed for each disease type. RESULTS: Relative risks were significantly greater than 1.0 for venous thromboembolism (RR = 2.8, CI = 2.4 to 3.2), stroke (RR = 1.8, CI = 1.6 to 2.0), and myocardial infarction (RR = 1.6, CI = 1.4 to 1.8), but not for death due to any cardiovascular cause (RR = 1.0, CI = 0.8 to 1.3). Study characteristics were diverse, and potential biases were frequently uncontrolled. For three of ten study characteristics identified as independently influencing relative risk, methodologically stronger studies of venous thromboembolism tended to have higher RRs. The RRs for stroke and myocardial infarction were lower in studies that were methodologically stronger with regard to variables identified as important. In studies of cardiovascular death, bias-control standards identified as important were generally well addressed by the studies. CONCLUSIONS: Oral contraceptive use does not appear to increase overall cardiovascular mortality. The associations noted with stroke and myocardial infarction may be due to methodologic flaws in the studies, while the association with venous thromboembolism is more likely to be valid.

Bias↗
PubMed1992

A meta-analysis of individualized instruction in dental education.

Although several dozen studies on individualized instruction in dental education have been conducted over the past 30 years, little has been done to summarize quantitatively these studies. The present investigation used Glass' techniques of meta-analysis to integrate statistically findings from 34 comparative studies on individualized instruction. A majority of these studies favored individualized over conventional instruction. The overall magnitude of effect, however, was small to moderate. One study characteristic variable--pacing of instruction--related significantly to effect size, with instructor-paced versions of individualized instruction producing larger achievement gains than student-paced versions. On average, individualized courses required only three-quarters of the time needed for conventional teaching. The results suggest that more research is needed in this area, particularly concerning applications of computer-based instruction, to assess adequately the potential of individualized modes of instruction for dental education.

Computer-Assisted Instruction↗
PubMed1992

A survey of instructional technology in dental education.

Little is known about current use of hardware and non-hardware instructional technologies in dental education. To address this area, the investigators designed a questionnaire to assess support for the development of instructional technology and determine the extent to which different instructional technologies are used in North American dental schools. Responses were received from 59 of 65 dental schools (91 percent). Respondents at most schools judged the administration at their school to be supportive of the development of instructional technology, but in general, did not feel faculty were enthusiastic about or rewarded for developing innovative methods. The most common computer-based application involves testing and record keeping, which is used extensively in about half the dental schools. Individualized instruction and paper and pencil simulations are used in at least some courses at a majority of dental schools. Schools with available support services apply certain technologies to a significantly greater extent than schools without available support services.

Canada↗
PubMed1991

Effectiveness of student ratings feedback and consultation for improving instruction in dental school.

The effects of student ratings feedback and consultation on instructional improvement over a four-year time interval were examined. Of the 40 course directors who led the same course over a four-year period, nine sought consultation services after receiving results from their initial student course evaluation. A sample of nine course directors who received student ratings feedback but did not seek consultation were matched to this consultation group, and student ratings comparisons were made over the subsequent three-year period. The consultation group received significantly higher ratings than the ratings only group for six of the nine course rating items. The magnitude of these effect sizes were substantial. When viewed in light of previously reported controlled studies on feedback, the results suggest that consultation is an important adjunct to ratings feedback for improving subsequent instruction in dental education. In response to an attitudinal survey, course directors indicated that students were qualified to rate aspects of instruction and that ratings provided useful feedback for making course improvements. Recommendations for using student ratings feedback are provided.

Analysis of Variance↗
PubMed1990

An evaluation of computer-based instruction versus printed study guides in a dental material course.

Although dental and allied dental educators increasingly use computer-based instruction (CBI), few studies have reported on its effectiveness. A study was designed to compare the effectiveness of CBI study guides with that of printed study guides in a dental materials course taught using Keller's Personalized System of Instruction (PSI). To evaluate the effectiveness of CBI versus printed study guides, student performance on unit mastery tests was assessed by means of chi-square analyses. Overall, it was found that students using CBI study guides did not pass significantly more unit tests than those using printed study guides. It was found, however, that high-aptitude students using CBI study guides performed significantly better than high-aptitude students using printed study guides. Students gave high ratings to both printed and CBI study guides.

Adult↗
PubMed1988

Workload and student course ratings in dental school.

Many faculty members express concern that the workload or difficulty of a course influences student ratings of the course. Research conducted in this area, however, shows that greater workloads are associated with higher course ratings and the workload/difficulty dimension of teaching does not seem to constitute a bias in student ratings. This study examined the extent to which workload was related to dental student course ratings. Over a three-year period, student course ratings were collected in 191 didactic courses. Based on student ratings of comparative workload, these courses were categorized as having high, medium, or low workloads. Courses with low workloads received significantly higher ratings from students for 11 of the 13 rating items. In contrast to previous research at the undergraduate level, student ratings in the dental school were significantly affected by the workload of a course. In the dental school setting, therefore, workload may serve as a biasing factor of student ratings. These findings have implications for providing rating feedback to course directors, administrators, and curriculum committees.

Attitude↗
PubMed1987

Quantitatively reviewing the literature: the application of meta-analysis.

Meta-analysis has evolved as an alternative to the conventional narrative review. Its purpose is to statistically analyze a large collection of results from multiple studies in order to integrate the findings. There are three basic components of meta-analytic methodology. Inclusiveness involves the location of studies and decisions regarding which studies to include in the analysis. Quantification refers to the expression of such outcomes as effect sizes and the coding of study characteristics. Integrating outcomes involves the pooling of results from individual studies. Critics of meta-analysis have focused on aspects of the methodology, but careful meta-analytic procedure protects against most potential biases. The methodological and statistical rigor of meta-analysis pressures us to conceptualize our research more clearly and report results more completely.

Data Interpretation, Statistical↗
PubMed1987

Teaching dental materials using the personalized system of instruction.

Tailoring instruction to the individual needs of students is one approach to ensuring that students with lower scholastic aptitudes obtain the skills and knowledge necessary to function successfully as professionals. This study determined the effects of the personalized system of instruction (PSI) on end-of-course achievement, aptitude-achievement relationships, long-term retention, and course attitudes. The PSI method of instruction was compared to a conventional lecture/laboratory approach for teaching a dental materials course to dental hygiene students. Although there was no significant difference between conventionally taught and PSI students on the end-of-term final examination, lower aptitude students in the PSI class scored significantly higher on the final examination than lower aptitude students in the conventional class. Of students completing a one-year retention examination, those in the PSI class scored significantly higher than students in the conventionally taught class. Student course ratings favored PSI instruction both at the end of the course and at the one-year follow-up interval.

Achievement↗
PubMed1984

Human IgE synthesis in vitro by pokeweed mitogen-stimulated human lymphoid cells: verification with a reconfirmed epsilon-specific radioimmunoassay.

This study was performed to address the controversy concerning human IgE biosynthesis in vitro induced by stimulation with pokeweed mitogen (PWM) or other agents. The controversy has focused on the specificity of reagents employed for quantitatively determining human IgE in culture supernatant fluids. Specifically, questions have been raised as to whether certain anti-human IgE antibody reagents possess anti-idiotypic reactivities, thereby resulting in reactions with Fab determinants of polyclonal immunoglobulins which would yield false-positive readings of IgE protein levels. We present a detailed analysis confirming that the goat anti-human IgE antibody designated GAHE(PS), which was initially isolated by affinity chromatography with the same IgE(PS) myeloma protein used for immunization, binds poorly, if at all, with IgG, IgA, or IgM immunoglobulins, even at excessive concentrations (100 micrograms/ml). Moreover, GAHE(PS) displayed no reactivity with Fab fragments of IgG or free L-chains prepared from pooled polyclonal IgG isolated from Cohn fraction II. A second GAHE reagent was prepared by purification by affinity chromatography on a second, completely unrelated IgE myeloma protein (DZA), which differed from IgE(PS) in light chain class, thereby resulting in a reagent, designated GAHE(DZA), which was completely devoid of any possible reactivity with L-chain or idiotypic determinants affiliated with IgE(PS). By utilizing both reagents, the studies presented here confirmed that PWM-stimulated human lymphoid cell cultures synthesize increased quantities of IgE, which can be detected in comparable amounts by both GAHE(DZA) and GAHE(PS) in supernatant fluids from such cultures. Because incorporation of the reversible protein synthesis inhibitor, cycloheximide, totally abolished the PWM-induced increases in IgE levels in such cultures, these results verify that such increases reflect de novo synthesis of human IgE as a result of PWM stimulation in vitro.

Animals↗