Statistics and Probability Commons^™

Assessing The Accuracy Of A New Diagnostic Test When A Gold Standard Does Not Exist, Todd A. Alonzo, Margaret S. Pepe

UW Biostatistics Working Paper Series

Often the accuracy of a new diagnostic test must be assessed when a perfect gold standard does not exist. Use of an imperfect test biases the accuracy estimates of the new test. This paper reviews existing approaches to this problem including discrepant resolution and latent class analysis. Deficiencies with these approaches are identified. A new approach is proposed that combines the results of several imperfect reference tests to define a better reference standard. We call this the composite reference standard (CRS). Using the CRS, accuracy can be assessed using multistage sampling designs. Maximum likelihood estimates of accuracy and expressions for …

A Pilot Study Testing A Proprietary Sealant For Plaque Reduction, Jennifer Rowland

Loma Linda University Electronic Theses, Dissertations & Projects

Enamel demineralization due to increased plaque accumulation is a well-recognized problem associated with fixed orthodontic appliances. The purpose of this study was to evaluate the efficacy of a proprietary product to be marketed by 3M Unitek for the reduction of plaque accumulation and thereby reduce enamel demineralization.

Sixty four bovine teeth were divided equally into an untreated control group and a group treated with the proprietary sealant product. Both groups were subsequently immersed in a Streptococcus mutans culture. Plaque deposits from each group were removed, suspended in trypticase soy broth, serially diluted, and plated on trypticase soy agar at 1, …

Does The Oswestry Or Sf-36 Help A Therapist To Predict Treatment Classification, Amy Crawford, Denese D. Kaufeldt-Soliz

Loma Linda University Electronic Theses, Dissertations & Projects

The purpose of this study was to determine the relationship of two disability questionnaires, the Oswestry Low Back Pain Disability Questionnaire (Oswestry) and the Medical Outcome Study Short Form-36 (SF-36), and a standardized physical examination and diagnostic classification system. The physical examination was performed by the evaluating therapists from the clinic and classification was determined by the evaluating therapists and the investigators to ensure correct subject placement into treatment Stages la, lb, or II. Data collection occurred at an outpatient physical therapy clinic in a metropolitan area health maintenance organization, where a sample of 221 subjects with low back pain …

A Longitudinal Study Of Hospitalization Rates For Patients With Chronic Disease: Results From The Medical Outcomes Study., Eugene C. Nelson, Colleen A. Mchorney, Willard G. Manning, W H. Rogers

Dartmouth Scholarship

To prospectively compare inpatient and outpatient utilization rates between prepaid (PPD) and fee-for-service (FFS) insurance coverage for patients with chronic disease. Data from the Medical Outcomes Study, a longitudinal observational study of chronic disease patients conducted in Boston, Chicago, and Los Angeles.A four-year prospective study of resource utilization among 1,681 patients under treatment for hypertension, diabetes, myocardial infarction, or congestive heart failure in the practices of 367 clinicians.

A Method Of Identifying Hazardous Highway Locations Using The Principle Of Individual Lifetime Risk, Paul J. Ossenbruggen

RISK: Health, Safety & Environment (1990-2002)

Dr. Ossenbruggen presents a scientific framework for identifying hazardous highway locations that may be more easily understood by non-scientists and has potential for comparing highway with other risks to health.

A Cephalometric Study Of The Class Ii Correction Effects Of The Eureka Spring, Ernest L. Stromeyer

Loma Linda University Electronic Theses, Dissertations & Projects

The effect of the Eureka Spring appliance, was investigated on 37 consecutively treated, non compliant, bilateral Class II malocclusions, requiring at least 3 mm or more of additional molar correction. The mean pretreatment age of this sample was 13.9 years. All patients were treated by a single clinician utilizing the Eureka Spring. Lateral cephalographs were taken at start of orthodontic treatment (T1), at insertion of Eureka Springs (T2), and at removal of the Eureka Springs (T3). The average treatment interval between T2 and T3 was 4 months. Class II correction occurred almost entirely by dentoalveolar movement, 33% in the maxilla …

An Administrative View Of Model Uncertainty In Public Health, Clark D. Carrington

RISK: Health, Safety & Environment (1990-2002)

Dr. Carrington reviews several ways to deal with model uncertainty, including those failing to acknowledge any use of models. He then evaluates six such methods with regard to, e.g., transparency and cost of execution.

A New Soft Tissue Analysis : To Establish Facial Esthetic Norms In Young Adult Females, Anne Béress

Loma Linda University Electronic Theses, Dissertations & Projects

Two hundred and fifty-five articles, books, and masters theses were reviewed for the most frequently applied soft tissue measurements in the literature in order to develop a new soft tissue analysis computer program that includes established soft tissue measurements and the newly developed globe analysis. A meta analysis of 20 normal occlusion studies, was performed to obtain mean values and standard deviations to form a large sample size. Inclusion criteria for articles in the meta analysis were normal occlusion, no orthodontic treatment, pleasing faces, statement on age, race, and lip position of the population. For the lateral view, angular and …

Methodological And Substantive Issues In Substance Abuse Prevention Research, C. Anderson Johnson, John W. Farquhar, Steve Sussman

CGU Faculty Publications and Research

This article summarizes current issues in drug abuse prevention research through integration of other articles in this journal and by heeding historical trends in prevention science. Recommendations are made for future research directions. For prevention to advance, iterative processes are needed involving both quasi-experimental and experimental designs and involving both small, simple units and large, complex, interactive units. Accuracy of measurement and replication are of paramount importance.

Association Between Nutrient Intake And Risk Of Coronary Heart Disease In California Seventh-Day Adventists, Peter Pribiš

Loma Linda University Electronic Theses, Dissertations & Projects

Dietary habits are believed to be major determinants of risk of coronary heart disease (CHD). Studies of high and low risk populations have suggested several nutrients to be protective or hazardous against CHD. Most published work since 1984 on diet and CHD in the Adventist Health Study (AHS) population examined either foods or food groups. This study investigated ten nutrients as exposure variables and their relationship to CHD risk. A cohort of 23,616 nonsmoking, non-Hispanic white California Seventh-day Adventists was followed for six years beginning in 1976. Extensive dietary information was collected at baseline, as well as values of traditional …

Weighing Evidence In Sexual Abuse Evaluations: An Introduction To Bayes's Theorem, James Wood

Selected Works Temporary Series

This article introduces readers to Bayes' theorem, a simple mathematical formula that can illuminate general issues and assist evaluators in the field of child sexual abuse. The theorem is applied to a case study of sexual abuse allegations that arose during a custody dispute.

Weighing Evidence In Sexual Abuse Evaluations: An Introduction To Bayes's Theorem, James Wood

Departmental Papers (Psych)

This article introduces readers to Bayes' theorem, a simple mathematical formula that can illuminate general issues and assist evaluators in the field of child sexual abuse. The theorem is applied to a case study of sexual abuse allegations that arose during a custody dispute.

Sources Of Epidemiological Equivocacy, Timothy Sly

RISK: Health, Safety & Environment (1990-2002)

Mr. Sly discusses five sources of uncertainty and ambiguity in health and medical research that can interfere with decision making.

Mandibular Asymmetry In Unilateral Class Ii Malocclusion : A Cephalometric Study, Raed Z. Moussa

Loma Linda University Electronic Theses, Dissertations & Projects

The purpose of this study is to evaluate skeletal and dental asymmetry in unilateral class II malocclusion. A study group of 25 unilateral subdivision patients was compared to 25 class I malocclusion patients serving as the control group. Submento-vertical and frontal radiographs were used for the evaluation. Symmetry was evaluated by comparing measurements between right and left sides for both groups and matching the middle points with the midsagittal axis. Statistical paired and simple t-test were used to evaluate the difference between the two sides for both groups. The measurements showed no significant skeletal and dental asymmetries except for three …

Space Closure Efficiency With Modified Ceramic Brackets : A Comparative Study, Kirk A. Specht

Loma Linda University Electronic Theses, Dissertations & Projects

The purpose of this study was to determine if the rate of extraction site closure was determined by the type of ceramic bracket used. A new ceramic bracket with a metal archwire slot was compared with a conventional ceramic bracket. Twenty patients were randomly assigned the metal slot ceramic bracket and conventional ceramic to one half of their maxillary arch respectively. The distribution was even left and right.

Retraction was started and completed on an 0.016" stainless steel round continuous archwire. One hundred gram sentalloy springs provided a uniform retraction force and were reactivated every four weeks to maintain a …

Periodontal Repair In Dogs : Evaluation Of Rhbmp-2 Carriers, Lauralee Nygaard

Loma Linda University Electronic Theses, Dissertations & Projects

This study evaluated candidate carriers for recombinant human bone morphogenic protein-2 (rhBMP-2) in periodontal reconstructive surgery.

Canine demineralized bone matrix (DBM), bovine inorganic crystallene bone matrix (Bio-Oss), bovine derived microfibrillar collagen matrix (Helistat), poly (D,L-lactide-coglycolide) micropaiticles (PLGA), and polylactic acid granules (Drilac) were used with rhBMP-2 (20 (µg/100 µl implant volume) in routine critical size canine supraalveolar periodontal defects. Contralateral defects in six beagle dogs were randomly assigned to receive: DBM/rhBMP-2, DBM-control, Bio-Oss/rhBMP-2, Helistat/rhBMP-2, PLGA/rhBMP-2, or Drilac/rhBMP-2, all with autologous blood except for Helistat and PLGA. Animals were sacrificed eight weeks post-surgery and block sections of the defects were processed …

Student Evaluations Of Teaching Effectiveness: The Interpretation Of Observational Data And The Principle Of Faute De Mieux, B. Burt Gerstman

Faculty Publications

Student opinion surveys are important but widely misunderstood tools for evaluating teaching effectiveness. In this brief review, an analogy is drawn between the use and interpretation of observational data for public health and biomedical research and the use of student opinion data in evaluating teach ing effectiveness. Sources of systematic error in the form of selection bias, information bias, and confounding are defined and illustrated. Original data concerning intermittent "quid pro quo" confounding (i.e., the effect of expected grades on student evaluations of teaching) are presented. Finally, the principle of faute de mieux ("lack of anything better") and the interpretation …

The Relationship Of Dietary And Lifestyle Factors To Bone Mineral Density Of Healthy Singaporean Chinese Women, Ampai Dana Aimsiri

Loma Linda University Electronic Theses, Dissertations & Projects

Few studies have examined the risk factors associated with reduced bone mass in Asians, but none specifically investigated Singaporean Chinese women. The subjects in this study were 16 premenopausal, 8 perimenopausal and 13 postmenopausal women who participated in a larger study which began in 1986. Bone density was measured in 1986 and 1992. Dietary and lifestyle data were collected for this study by personal interview. Association between dietary and lifestyle factors and bone density variables and change in bone density at the end of the 6 year period were assessed by univariate regression analyses.

Postmenopausal women had significantly lower baseline …

Long-Term Posttreatment Upper Incisor Inclination : Relative To Facial Axis Angulation As A Measure For Incisor Placement, David Lawrence Sparks

Loma Linda University Electronic Theses, Dissertations & Projects

This study was designed to determine whether upper central incisor inclination approximated the facial axis, long-term, posttreatment, regardless of the initial malocclusion or immediate posttreatment incisor inclination. Lateral head films at pretreatment, immediate posttreatment and long-term posttreatment were traced and evaluated. The sample was divided into facial type. Angle classification and treatment type (extraction vs. non-extraction). Statistical analyses included means, standard deviations, confidence intervals, population t tests and chi-square tabulations.

The results revealed that the upper central incisor did not approximate the facial axis after a minimum of 7 years posttreatment. This failed to support the use of the facial …

Measurement Of Blood Flow In Reflected Muco-Gingival Tissue Flaps In Cats : Using The Radiolabeled Microsphere Method, Gary T. Wuchenrich

Loma Linda University Electronic Theses, Dissertations & Projects

Blood flow to the maxilla and mandible may vary due to differences in vascular supply and in physiologic, metabolic and pathologic conditions. In general it is accepted that oral tissues have an abundant blood supply; however, there is little information quantifying blood flow to these regions. In this study, the maxillary tissues were chosen to measure the blood flow in attached and reflected gingival tissue in adult cats using the radiolabeled microsphere method.

Sixteen cats with permanent dentition, clean mouths, and without inflamed gingiva upon visual inspection were used and divided into two groups. Group 1 consisted of six cats …

Identification Of Risk Factors Associated With Pulpal Disease, Shelley R. Aronson

Loma Linda University Electronic Theses, Dissertations & Projects

A few studies have identified etiologic factors in pulpal disease, but little is known about the odds ratios of factors associated with pulpal disease. Odds ratios are well established measures of the effects of exposure to a particular outcome, and are comparisons of exposure to non-exposure in cases versus controls. The purpose of this study was to compare exposure of individual teeth to hypothesized risk factors in endodontic cases and in controls. This case-control study consisted of a chart review of 301 endodontic cases and 301 controls. Caries, types of restorations, and periodontal disease were the most significant factors. With …

The Media, Risk Assessment And Numbers: They Don't Add Up, Sharon M. Friedman

RISK: Health, Safety & Environment (1990-2002)

Professor Friedman argues that, for risks to be reported accurately, journalism educators must help their students understand science, numbers and statistics.

Reproducibility Of Periodontal Probing, Su-Fang Wang

Loma Linda University Electronic Theses, Dissertations & Projects

This study evaluated reproducibility of periodontal probing by conventional manual and automated force-controlled electronic probes. A total of 1206 sites (6 sites per tooth including maxillary and mandibular incisor/canine, premolar, and molar sites) in 15 patients with history of moderate or advanced chronic periodontal disease were examined. Probings included probing pocket depths (PD), as well as probing attachment levels (PAL) from a reference stent. Measurements were recorded to the nearest 0.5 mm with both methods. Patients were examined twice, 7 to 10 days apart. At each visit, all sites were probed first with the conventional probe and then with the …

The Impact Of A Primary Health Care Training Program On Morbidity In Kiyeyi, Rural Uganda, 1986-1991 : An Evaluation Of The Uganda-Finland Health Care Program, Marja-Leena Salin

Loma Linda University Electronic Theses, Dissertations & Projects

This study examines the effects of primary health care education efforts in reducing the disease case rates of acute respiratory infections, diarrhoea, malnutrition and measles in a rural Ugandan population between 1986 and 1991.

The intervention, a health education program offered by the Kiyeyi Health Center staff, consisted of a 12-week intensive training for community health workers and traditional birth attendants. Follow-up and supervision took place at regular intervals and continuing education was arranged every other year. Beginning in 1986, this training program was introduced in the first of seven clusters of villages, then expanded successively on an annual basis …

A Non-Human Primate Model For Evaluating A Fenestration Corticotomy Technique, Philip G. M. Khng

Loma Linda University Electronic Theses, Dissertations & Projects

A study model has been designed to evaluate the effectiveness of a new fenestration corticotomy procedure in two non-human primates Macaca fasicularis.

The objective of this study was to evaluate the efficacy of a new conservative corticotomy procedure to facilitate dental translation using fenestrations. This pilot study compared treatment and control quadrants of each individual animal's maxilla and mandible with both having the same retraction appliance and force on the 2nd premolar following extraction of the 1st molars. The null hypothesis stated that there was no significant statistical difference between the new conservative corticotomy procedure (fenestrations) when compared with …

Diet And Colon Cancer Risk In The Population Of Thailand, Nithat Sirichotiratana

Loma Linda University Electronic Theses, Dissertations & Projects

Epidemiological studies have emphasized environmental influences, especially a diet high in animal fat and low in fiber, as major risk factors for colon cancer. In order to examine the relationship between dietary fat and fiber and occurrence of colon cancer, patient medical records from the National Cancer Institute between 1981-1991 were used for the first hospital-based case-control study of diet and colon cancer in Thailand. These records included a total of 168 cases and 357 controls. Data on the frequency consumption of various food items were obtained by using an existing food frequency questionnaire, completed as part of patient’s history …

Tracking Plasma Lactate Concentration In Vivo With A Catheter-Tip L-Lactate Sensor, Brett T. Weinzapfel, Mark D. Ball, Lee R. Waite, Nacer E. Abrouk, Shun P. Lim

Mathematical Sciences Technical Reports (MSTR)

To circumvent the problems of repeated blood sampling for in vitro analysis, a catheter-tip L-lactate sensor has been developed. The sensor was tested in anesthetized pigs (n=6). The sensor in vivo tracked the lactate concentration non-linearly, seeming to obey Michaelis-Menten kinetics. Calibration time was short, typically 1.5 min per lactate standard. Furthermore, time drift was small, typically -1.3% to -3.3% per hour of in vivo use.

An In Vitro Study Comparing The Conventional Step-Back Instrumentation Technique To A Combination Step-Back/Ultrasonic Technique, James A. Eberhardt

Loma Linda University Electronic Theses, Dissertations & Projects

Cleaning and shaping the root canal system is an important phase of endodontic therapy, and must be performed thoroughly and completely if successful root canal therapy is to be expected. A number of investigators have compared different methods of cleaning and shaping of the root canal system. The purpose of this study was to compare the effectiveness of the conventional step-back technique with that of a combination step-back/ultrasonic technique. This combination technique is a modification of the conventional step-back technique using an ultrasonic instrument alternately with hand instrumentation. Utilizing 40 canals from extracted human mandibular molar teeth with a curvature …

Soft Tissue Changes Of The Upper Lip Following Isolated Le Fort I Osteotomies, Kendall E. James

Loma Linda University Electronic Theses, Dissertations & Projects

Pre-operative (T-1) and post-operative (T-3) radiographs were obtained and traced for fifty-one non-growing patients who had undergone isolated Le Fort I osteotomies. These tracings were then digitized with the results arranged in a data file and subjected to statistical analysis. The purpose of this study was to establish ratios for certain hard to soft tissue movements that could be used to aid the clinician in post-surgical soft tissue profile prediction. The results showed that even though a large sample was used, individual patient variability remained high particularly in the horizontal directions. Most ratios found in this study were consistent with …

Condylar Angulations As Related To Submental-Vertex Radiographs, Jady L. Chiakowsky

Loma Linda University Electronic Theses, Dissertations & Projects

Pretreatment submental-vertex radiographs were obtained for 637 adolescent patients (307 males, 330 females) who had presented themselves for orthodontic treatment. The purpose of this study was to: (1) determine the relationship between condylar angulations and depth of cut with the variables: age, sex, and race, and (2) establish normative values for the categories studied. The results indicated that no significant differences existed between the condylar angulations for the variables measured. However, significant differences did exist between the depth of cut for the variables measured and there was significant interaction between age and race with respect to the depth of cut. …