The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Frank Z Stanczyk - One of the best experts on this subject based on the ideXlab platform.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC women's health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC Women's Health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:Background: There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Methods: Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Results: Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Conclusions: Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
Andrew E Williams - One of the best experts on this subject based on the ideXlab platform.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC women's health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC Women's Health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:Background: There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Methods: Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Results: Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Conclusions: Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
Adrian A. Franke - One of the best experts on this subject based on the ideXlab platform.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC women's health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC Women's Health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:Background: There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Methods: Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Results: Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Conclusions: Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
Gertraud Maskarinec - One of the best experts on this subject based on the ideXlab platform.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC women's health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
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The temporal reliability of serum estrogens, progesterone, gonadotropins, SHBG and urinary estrogen and progesterone metabolites in premenopausal women
BMC Women's Health, 2002Co-Authors: Andrew E Williams, Gertraud Maskarinec, Adrian A. Franke, Frank Z StanczykAbstract:Background: There is little existing research to guide researchers in estimating the minimum number of measurement occasions required to obtain reliable estimates of serum estrogens, progesterone, gonadotropins, sex hormone-binding globulin (SHBG), and urinary estrogen and progesterone metabolites in premenopausal women. Methods: Using data from a longitudinal study of 34 women with a mean age of 42.3 years (SD = 2.6), we calculated the minimum number of measurement occasions required to obtain reliable estimates of 12 analytes (8 in blood, 4 in urine). Five samples were obtained over 1 year: at baseline, and after 1, 3, 6, and 12 months. We also calculated the percent of True Variance accounted for by a single measurement and intraclass correlation coefficients (ICC) between measurement occasions. Results: Only 2 of the 12 analytes we examined, SHBG and estrone sulfate (E1S), could be adequately estimated by a single measurement using a minimum reliability standard of having the potential to account for 64% of True Variance. Other analytes required from 2 to 12 occasions to account for 81% of the True Variance, and 2 to 5 occasions to account for 64% of True Variance. ICCs ranged from 0.33 for estradiol (E2) to 0.88 for SHBG. Percent of True Variance accounted for by single measurements ranged from 29% for luteinizing hormone (LH) to 92% for SHBG. Conclusions: Experimental designs that take the natural variability of these analytes into account by obtaining measurements on a sufficient number of occasions will be rewarded with increased power and accuracy.
Ad Ridder - One of the best experts on this subject based on the ideXlab platform.
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Tail distribution of the maximum of correlated Gaussian random variables
2015 Winter Simulation Conference (WSC), 2015Co-Authors: Zdravko I. Botev, Michel Mandjes, Ad RidderAbstract:In this article we consider the efficient estimation of the tail distribution of the maximum of correlated normal random variables. We show that the currently recommended Monte Carlo estimator has difficulties in quantifying its precision, because its sample Variance estimator is an inefficient estimator of the True Variance. We propose a simple remedy: to still use this estimator, but to rely on an alternative quantification of its precision. In addition to this we also consider a completely new sequential importance sampling estimator of the desired tail probability. Numerical experiments suggest that the sequential importance sampling estimator can be significantly more efficient than its competitor.
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Winter Simulation Conference - Tail distribution of the maximum of correlated gaussian random variables
2015 Winter Simulation Conference (WSC), 2015Co-Authors: Zdravko I. Botev, Michel Mandjes, Ad RidderAbstract:In this article we consider the efficient estimation of the tail distribution of the maximum of correlated normal random variables. We show that the currently recommended Monte Carlo estimator has difficulties in quantifying its precision, because its sample Variance estimator is an inefficient estimator of the True Variance. We propose a simple remedy: to still use this estimator, but to rely on an alternative quantification of its precision. In addition to this we also consider a completely new sequential importance sampling estimator of the desired tail probability. Numerical experiments suggest that the sequential importance sampling estimator can be significantly more efficient than its competitor.