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Biomedical subjects

B Bull

Publications and source records attributed to B Bull.

At least 19 recordsLinked to original sources
PubMed1998

Approximate standard errors and confidence intervals for indices of positive and negative agreement.

Indices of positive and negative agreement for observer reliability studies, in which neither observer can be regarded as the standard, have been proposed. In this article, it is demonstrated by means of an example and a small simulation study that a recently published method for constructing confidence intervals for these indices leads to intervals that are too wide. Appropriate asymptotic (i.e., large sample) variance estimates and confidence intervals for the positive and negative agreement indices are presented and compared with bootstrap confidence intervals. We also discuss an alternative method of interval estimation motivated from a Bayesian viewpoint. The asymptotic intervals performed adequately for sample sizes of 200 or more. For smaller samples, alternative confidence intervals such as bootstrap intervals or Bayesian intervals should be considered.

Confidence Intervals↗
PubMed1991

A national profile of school-based transition programs for deaf adolescents.

In this study, the transition programs of 326 secondary educational programs for deaf and severely hearing-impaired adolescents were surveyed. Three types of programs were surveyed: residential, mainstream, and "other" (a combination of the first two programs). Sixty-four items depicting desirable transition characteristics were included in the survey, and each item was rated by the programs on a value scale and an implementation scale. Analyses of variance were calculated to determine if there were statistically significant differences among the three program types for each individual survey item on the two rating scales. Based on the data, it appears that the residential schools had higher implementation rates than the mainstream and other programs. All three respondent groups valued the transition items more than they had implemented them (i.e., the value scores were higher than the implementation scores). The data point out the need for researchers and educators to develop and implement more effective transition programs for deaf and severely hearing-impaired students.

Adolescent↗
PubMed1987

Calibration of hematology analyzers. Role of the microhematocrit.

Discrepancies between the hematocrit values measured by automated methods and those measured by centrifugation have discouraged the use of the centrifuged microhematocrit to calibrate automated hematology analyzers. The discrepancy appears to be due to changes in the internal viscosity of red blood cells and can be eliminated in the most popular line of automated whole blood analyzers (Coulter Counters) by use of a simple correction table. Fresh blood obtained from volunteers was separated by centrifugation into fractions of increasing mean corpuscular hemoglobin concentration. A correction table for hematocrit values obtained by automated equipment was derived from the linear relationship between the discrepancy in hematocrit values and the manually obtained values for mean corpuscular hemoglobin concentration. With the use of the correction table, an average of three randomly selected fresh blood samples is sufficient to transfer a centrifugally determined hematocrit value to a multichannel analyzer with a coefficient of variation of 1.5%. Thus, this straightforward approach permits the microhematocrit to function as a practical calibration standard.

Autoanalysis↗
PubMed1980

Whither the WBC differential?--some alternatives.

Most efforts to automate the WBC differential have involved the use of devices to identify and enumerate WBC types, the underlying assumption being that the cell type percentages constitute the important end results. A different assumption exists. It is that the clinical usefulness of this procedure derives primarily from the fact that a trained morphologist has conducted a detailed examination of the slide. Based on this second assumption, a different approach to automation was investigated. This involved the use of a computer system to augment the morphologist in the slide examination process. This augmentation was accomplished by: 1. Determination of linked abnormalities on 117,000 WBC counts and presentation of linkages to the morphologist when a particular abnormality was identified on the hemogram or the slide. 2. Information feedback which compared each technologist with others in the laboratory performing similar tasks. 3. Varying the number of cells examined per slide, based on the apparent abnormality of the slide. The linkage patterns found, their clinical usefulness, and the impact on technologist performance and test quality are discussed.

Computers↗