Sample sizes for constructing confidence intervals and testing hypotheses.
Explore the source record for details and available documents.
Data Interpretation, Statistical↗
Biomedical subjects
D Seigel
Publications and source records attributed to D Seigel.
Surrogate endpoints in clinical trials: ophthalmologic disorders.
We examined three examples of surrogate observations in ophthalmology. The first represents a simple case: the status of one eye is used as a surrogate for the (unobservable) status of the opposite eye in the same individual. The second and third examples represent possible extrapolation of long term results on the basis of early changes. These examples are used to illustrate the assumptions intrinsic in the use of surrogate variables.
Clinical Trials as Topic↗
Grading of images in a clinical trial.
We developed a computer model to compare the power in clinical trials that use either of two grading schemes for objectively recorded dependent variables. The example we use is an eye lens photo. The first grading system consists of side by side comparison of the before and after treatment photos; the second involves separate grading of the two photos. This modelling experience suggests that separate grading may often yield more power than side by side comparison, and offers other advantages as well. For applications in which grading error is considerably smaller in the side by side method, power may be markedly better. Most importantly, strong prejudice in favour of one or the other approach in all situations seems unwarranted.
Cataract↗
Designs for clinical research.
Explore the source record for details and available documents.
Clinical Trials as Topic↗
Analysis of follow-up data.
Explore the source record for details and available documents.
Follow-Up Studies↗
Survival rates after enucleation of eyes with malignant melanoma.
We investigated the rates of mortality for several types of malignant melanomas for evidence that surgery accelerates metastasis. Additionally, we reanalyzed uveal melanoma survival rates from the Armed Forces Institute of Pathology. Our computations showed higher death rates in years two to five after diagnosis than in years one or six to ten. The same pattern of a peak mortality in the early years after diagnosis and lower rates six to ten years thereafter was seen in all tumor types studied. Our analysis of survival rates produced no evidence to alter the existing pattern of treatment for malignant melanoma of the uvea.
Eye Neoplasms↗