ESTIMATION OF BLOOD-PLATELET SURVIVAL .6. EVALUATION OF GRAPHICAL METHOD

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 143  (2) , 25-31
Abstract
An experiment was performed in which 13 scientists experienced in analyzing data on platelet survival were sent blind duplicate sets of 10 platelet survival curves and requested to fit the best straight line through the data by eye and determine its point of intersection with the time axis. The duplicate sets labeled control and aspirin, respectively, were artificial data generated from evaluation for various times of a .gamma. curve of order 5 and adding random independent normal (Gaussian) errors having a SD of 0.03. The results were analyzed to examine inter- and intra-observer variance, reproducibility and bias. The range of means of estimated survival was 8.68 days-11.59 days and in the control data showed about 63 times as much variance among observers as that due to random error of measurement alone. The aspirin data showed similar results. Correlation coefficients within observers for the pairs of estimates varied from -0.307 to +0.920. Three observers showed strong systematic differences between the duplicate readings. Formal, rather than graphical, analysis of the data is needed.