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PubMed1984

Clinical hypothesis testing in family practice: a biopsychosocial perspective.

Recent studies of the clinical problem-solving process have demonstrated the importance of hypothesis generation and testing in shaping the nature of information gathering, differential diagnosis, and therapeutic decision making. Family physicians and other primary care physicians are often faced with complex and undifferentiated illness problems that require them to go beyond the traditional biomedical model and entertain an expanded range of psychosocial hypotheses. In this paper the authors draw upon clinically relevant behavioral and social science research and propose several biopsychosocial hypotheses that have proven useful in the management of family practice patients. Seven illustrative case studies are presented, and some implications of this biopsychosocial paradigm for practice, research, and teaching are discussed.

Adolescent↗
PubMed1980

Interpretation of research data: hypothesis testing.

The application of statistical tests to the evaluation of hypotheses is discussed. The statistical test is used to determine whether or not a hypothesis is correct by telling the researcher how likely it is that the results of an experiment are due to chance alone. Generally, a null hypothesis is set up stating that there is no difference between the control and experimental samples. The data are than collected and analyzed, and the null hypothesis is either accepted or rejected. The researcher, before beginning actual experimentation, should establish a level of significance to indicate how certain he wishes to be that the results are not due to chance alone. Traditionally, this level is set at 95% or 99% (expressed as a level of significance of 0.05 or 0.01, respectively). In using these tests, two types of error are possible. The null hypothesis can be rejected when it is in fact true (Type I error), or it can be accepted when it is false (Type II error). Since all statistical tests are based on certain assumptions concerning the data, the test applied to experimental results must be chosen to fit the data (e.g., collection methods, distribution type). for these reasons, statistical tests should be chosen before the experiment, and the experimental procedures should be tailored to fit the statistical test so that the validity of the analysis will be maximized.

Analysis of Variance↗
PubMed1996

Hypothesis testing and earthquake prediction.

Requirements for testing include advance specification of the conditional rate density (probability per unit time, area, and magnitude) or, alternatively, probabilities for specified intervals of time, space, and magnitude. Here I consider testing fully specified hypotheses, with no parameter adjustments or arbitrary decisions allowed during the test period. Because it may take decades to validate prediction methods, it is worthwhile to formulate testable hypotheses carefully in advance. Earthquake prediction generally implies that the probability will be temporarily higher than normal. Such a statement requires knowledge of "normal behavior"--that is, it requires a null hypothesis. Hypotheses can be tested in three ways: (i) by comparing the number of actual earth-quakes to the number predicted, (ii) by comparing the likelihood score of actual earthquakes to the predicted distribution, and (iii) by comparing the likelihood ratio to that of a null hypothesis. The first two tests are purely self-consistency tests, while the third is a direct comparison of two hypotheses. Predictions made without a statement of probability are very difficult to test, and any test must be based on the ratio of earthquakes in and out of the forecast regions.

Journal Article↗
PubMed1994

Efficient use of biological banks for biochemical epidemiology: exploratory hypothesis testing by means of a sequential t-test.

In view of recent advances in molecular and biochemical epidemiology, there is growing interest in the creation of biological banks of blood, urine, tissue, or other biological specimens collected from participants in prospective cohort studies. The existence of biological banks may make it possible to study a multitude of etiologic hypotheses, by comparing biochemical parameters measured in the biological specimens of subjects who will eventually develop the disease of interest ("cases") and of control subjects, using a nested case-control or a case-cohort design. In practice, however, the amount of biological material available per subject (in particular, that of cases) will limit the number of hypotheses that can be tested. The present paper discusses the use of a sequential t-test which, compared with an analogous fixed sample procedure, will on average require fewer biological specimens before a given study hypothesis can be accepted or rejected. The sequential test should thus facilitate an early decision on whether a new hypothesis is worth further investigation, while avoiding wasting too much biological material on testing hypotheses that may eventually prove unfruitful. If the test reveals an exposure difference of interest, the study may be extended so that relevant epidemiologic effect measures can be estimated more accurately.

Biological Specimen Banks↗
PubMed1997

Hypothesis testing and effect size estimation in clinical trials.

LEARNING OBJECTIVES: This paper provides the reader with an overview of several key elements in study planning and analysis. In particular, it highlights the differences between significance tests (statistical significance) and effect size estimation (clinical significance). DATA SOURCES: This paper focuses on methodologic issues, and provides an overview of trends in research. PAPER SELECTION: References were selected to provide a cross-section of the approaches currently being used. The paper also discusses a number of logical fallacies that have been cited as examples in earlier papers on research design. CONCLUSIONS: Significance tests are intended solely to address the viability of the null hypothesis that a treatment has no effect, and not to estimate the magnitude of the treatment effect. Researchers are advised to move away from significance tests and to present instead an estimate of effect size bounded by confidence intervals. This approach incorporates all the information normally included in a test of significance but in a format that highlights the element of interest (clinical significance rather than statistical significance). This approach should also have an impact on study planning--a study should have enough power to reject the null hypothesis and also to yield a precise estimate of the treatment effect.

Clinical Trials as Topic↗
PubMed1976

The psychiatric examination in the walk-in clinic. Hypothesis generation and hypothesis testing.

Rapid assessment for decision making is a major goal of the initial psychiatric interview in walk-in clinics, emergency psychiatric services, and the ambulatory services of community mental health centers. To accomplish this task, the clinician must learn to elicit specific data to confirm or refute clinical hypotheses rather than gather a complete history. This report, in formulating a hypothesis generating and testing approach for the initial psychiatric examination, proposes 16 hypotheses that organize the clinical data necessary for most decisions. This approach is intended to help the clinician make efficient use of limited time, guard him from coming to premature closure in the collection of data, and provide a stimulus for the exploration of relevant but neglected clinical questions.

Affective Symptoms↗
PubMed1990

Tracing the footsteps of Sherlock Holmes: cognitive representations of hypothesis testing.

A well-documented phenomenon in opinion-revision literature is subjects' failure to revise probability estimates for an exhaustive set of mutually exclusive hypotheses in a complementary manner. However, prior research has not addressed the question of whether such behavior simply represents a misunderstanding of mathematical rules, or whether it is a consequence of a cognitive representation of hypotheses that is at odds with the Bayesian notion of a set relationship. Two alternatives to the Bayesian representation, a belief system (Shafer, 1976) and a system of independent hypotheses, were proposed, and three experiments were conducted to examine cognitive representations of hypothesis sets in the testing of multiple competing hypotheses. Subjects were given brief murder mysteries to solve and allowed to request various types of information about the suspects; after having received each new piece of information, subjects rated each suspect's probability of being the murderer. Presence and timing of suspect eliminations were varied in the first two experiments; the final experiment involved the varying of percentages of clues that referred to more than one suspect (for example, all of the female suspects). The noncomplementarity of opinion revisions remained a strong phenomenon in all conditions. Information-search data refuted the idea that subjects represented hypotheses as a Bayesian set; further study of the independent hypotheses theory and Shaferian belief functions as descriptive models is encouraged.

Adult↗
PubMed1996

The force requirements for tooth movement. Part III: The pressure hypothesis tested.

Many experiments have investigated the force requirements for tooth movement; the diverse results so obtained have lead to controversy and resulted in an incomplete understanding of the true nature of tooth movement. This study analyses the results of two experiments which investigated the relation between the force applied and the rate of tooth movement from the standpoint of the pressures exerted by the tooth root on the surrounding tooth-periodontal membrane complex. The pressure hypothesis suggested by Smith and Storey is tested using the estimated projected area of the teeth moved in the experiments as a means of calculating the estimated pressures resulting from the application of orthodontic forces. The average pressure at which optimal rates of tooth movement occurred in these experiments was 197 gf cm-2.

Adolescent↗
PubMed2002

Implicit and explicit processes in a hypothesis testing task.

We present the results of two experiments investigating the factors that determine responding on the pseudo-diagnosticity task. In Expt 1 we manipulated people's beliefs about the degree to which an initial piece of evidence supported a focal hypothesis and found decreased pseudo-diagnostic (PD) responding when the evidence offered low support for the focal hypothesis. In Expt 2 we manipulated the instructions given to participants. We found that instructions to select evidence to help decide between the focal and the complementary hypotheses produced fewer PD responses than both instructions to decide whether the focal hypothesis was the case and instructions to decide whether its complement was the case. The results are interpreted within the framework of recent dual process theories of reasoning.

Adolescent↗
PubMed1976

An assessment of hypothesis testing in mentally retarded adolescents.

Groups of educable and trainable institutionalised retarded adolescents were tested on a discrimination learning problem with a modified blank trials procedure in an attempt to measure their hierarchy of hypotheses. Results indicated that the hierarchy and size of initial hypothesis sets varied as a function of degree of retardation. Trainable retarded subjects had fewer hypotheses, and initially chose position hypotheses predominantly. Under discriminate reinforcement, most of these were readily switched to stimulus dimension hypotheses, which they retained during additional non-discriminate (100 per cent) reinforcement trials. Educable retarded subjects predominantly chose stimulus dimension hypotheses initially, and most of these switched to position hypotheses during either discriminate or non-discriminate reinforcement trials.

Adolescent↗
PubMed2000

Multiple data sets, congruence, and hypothesis testing for the phylogeny of basal groups of the lizard genus Sceloporus (Squamata, Phrynosomatidae).

Several data partitions, including nuclear and mitochondrial gene sequences, chromosomes, isoenzymes, and morphological characters, were used to propose a new phylogeny and to test previously published hypotheses about the phylogenetic positions of basal clades of the lizard genus Sceloporus and the relationship of Sceloporus to the former genus "Sator". In accord with earlier studies, our results grouped "Sator" as internal to Sceloporus, and both support a hypothesis of transgulfian vicariance for the origin of the former genus "Sator" on islands in the Sea of Cortez. Robustness of support for internal nodes in our best tree was established though widely used indices (bootstrap proportions, decay values) but also through congruence among independent data partitions. Several deep nodes in the tree recovered by several methods, including equally weighted and differentially weighted parsimony and maximum likelihood models, are only weakly supported by the traditional indices. This methodological concordance is taken as evidence for insensitivity of the deep structure of the topology to alternative assumptions.

Animals↗
PubMedDate not supplied

A strategy for introducing diagnostic reasoning: hypothesis testing using a simulation approach.

The ability to generate a number of hypotheses, so all possibilities in a situation are recognized, is a vital component in arriving at a correct nursing diagnosis. Students need learning experiences in this aspect of the diagnostic reasoning process. The authors discuss the four phase simulation method of teaching, which provides a useful model for developing beginning skills in hypothesis generation.

Clinical Competence↗
PubMedDate not supplied

Hypothesis testing in the polychotomous logistic model with an application to detecting gastrointestinal cancer.

We discuss the use of the trichotomous logistic model to discriminate between patients with gastrointestinal (GI) cancer, patients with benign GI disease and 'normal' subjects, using symptoms and the concentrations of some serum proteins that are potentially indicative of malignancy as covariates. A parsimonious model can be obtained by invoking an indistinguishability hypothesis which is appropriate when a covariate is considered to have no predictive value between categories. It is shown that the polychotomous model can be re-parameterised under the null hypothesis to give a 'reduced form', which can be fitted by maximum likelihood. The validity of the use of the same methods for retrospective sampling is discussed. The approach is illustrated by the development of a logistic model to identify symptomatic and asymptomatic subjects with a high risk of GI cancer.

C-Reactive Protein↗
PubMed1998

A neglected window on hypothesis testing in adolescence: explicit standard order conditional selection tasks.

The paper reported four experiments on explicit standard order conditional selection tasks, which permit more direct inference of subjects' strategies than do other conditional selection tasks. The experiments allowed plausible rational support-seeking strategies to be reduced from nine to three, disproof strategies from six to three. The main strategy in early adolescence was either (1) models-based deduction, as suggested by Johnson-Laird and Byrne in 1991 or (2) rules-based deduction, as suggested by Rips in 1994, with a factual attitude to hypothesis and offered information. In late adolescence a substantial minority adopt a hypothetical attitude to both these things, which may be applied with either of these strategies or with (3) the nondeductive strategy suggested by Langford and Hunting in 1994. This general picture of developmental possibilities can be extended to Inhelder's and Piaget's problems requiring information search to test conditional and biconditional hypotheses, in particular their chemicals, pendulum, and rods problems. This extension is obtained by assuming that adolescents acquire a range of strategies for problems requiring more or less focussed information search, conditional selection tasks requiring the former, Piagetian formal operations tasks tending towards the latter. Current evidence does not indicate whether strategies (1) or (2) are dominant in younger adolescents or whether strategies (1) or (2) or (3) are dominant in older adolescents. Thus, the Piagetian argument that formal operations thinking passes from factual rules-based deduction to hypothetical rules-based deduction is only one of several styles of theory that can readily accommodate current evidence in this area.

Adolescent↗
PubMed1996

A new approach to studying modern human origins: hypothesis testing with coalescence time distributions.

A new approach for testing hypotheses about modern human origins using molecular divergence dates is presented. Coalescence times from many unlinked loci are needed to test the alternative models. Hypotheses are evaluated on the basis of their differing predicted distribution patterns of coalescence times from multiple genes. No single coalescence time from one genetic system is sufficient to reject any of the three alternative models. Several nuclear datasets give recent dates for human genetic ancestors, at approximately the mitochondrial coalescence time, while some nuclear datasets support older dates. Given the overall distribution of available mitochondrial and nuclear coalescence times, the rapid replacement hypothesis is the likeliest model for modern human origins. The unusual nature of the human mitochondrial pattern is highlighted by comparative data from nonhuman hominoids. To understand the pattern of modern human genetic variability better, more nuclear data from all hominoid species are needed.

Animals↗
PubMed2001

Hypothesis testing of the aging male gonadal axis via a biomathematical construct.

Neuroendocrine axes are feedback- and feedforward-coupled dynamic ensembles. Disruption of selected pathways in such networklike organizations may explicate loss of orderly hormonal output as observed in aging. To test this notion more explicitly, we implemented an earlier computer-assisted biomathematical model of the interlinked male hypothalamo [gonadotropin-releasing hormone (GnRH)]-pituitary [luteinizing hormone, (LH)]-testicular [Leydig cell testosterone (Te)] axis (Am J Physiol Endocrinol Metab Physiol 275: E157--E176, 1988; Keenan D., W. Sun, and J. D. Veldhuis, SIAM J Appl Math 61: 934--965, 2000). Thereby, we appraise mechanistic hypotheses for more disorderly LH and Te secretion in aging men. We compare model predictions with monitored abnormalities in the older male, namely, irregular patterns of individual and synchronous LH and Te release, reduced 24-h rhythmic Te output, and variably elevated LH secretion. Among the mechanisms examined, the most parsimonious aging hypothesis would entail impaired LH feedforward on Te without or with attenuated Te feedback on GnRH/LH secretion. This investigative strategy should aid in exploring new postulates of disrupted feedback networks in pathophysiology.

Adult↗
PubMed2000

Anticipation of oxidative damage decelerates aging in virgin female medflies: hypothesis tested by statistical modeling.

Empirical analysis of survival data obtained from large samples of Mediterranean fruit flies shows that the trajectory of the mortality rate for virgin females departs from that for females maintained in mixed sex cages. It increases, decelerates, reaches its maximum, declines and then increases again within the reproductive interval. Non-virgin females, however, display an early-age plateau instead of this dip. We assume that these deviations are produced by the interplay between changes in oxygen consumption associated with reproductive behavior and the antioxidant defense that acts against anticipated oxidative damage caused by reproduction. Since there are no data on antioxidant mechanisms in medflies available that explain the observed patterns of mortality, we develop a model of physiological aging based on oxidative stress theory, which describes age-related changes in oxygen consumption and in antioxidative capacity during the reproductive period. Using this model, we simulate virtual populations of 25,000 virgin and non-virgin flies, calculate the respective mortality rates and show that they practically coincide with those of experimental populations. We show that the hypothesis about the biological support of reproduction used in our model does not contradict experimental data. The model explains how the early-age dip and plateau might arise in the mortality rates of female medflies and why the male mortality pattern does not exhibit such deviations.

Aging↗