The paper aims to discuss three interesting issues of statistical inferences for a common risk ratio (RR) in sparse meta-analysis data. Firstly, the conventional log-risk ratio estimator encounters a number of problem...The paper aims to discuss three interesting issues of statistical inferences for a common risk ratio (RR) in sparse meta-analysis data. Firstly, the conventional log-risk ratio estimator encounters a number of problems when the number of events in the experimental or control group is zero in sparse data of a 2 × 2 table. The adjusted log-risk ratio estimator with the continuity correction points based upon the minimum Bayes risk with respect to the uniform prior density over (0, 1) and the Euclidean loss function is proposed. Secondly, the interest is to find the optimal weights of the pooled estimate that minimize the mean square error (MSE) of subject to the constraint on where , , . Finally, the performance of this minimum MSE weighted estimator adjusted with various values of points is investigated to compare with other popular estimators, such as the Mantel-Haenszel (MH) estimator and the weighted least squares (WLS) estimator (also equivalently known as the inverse-variance weighted estimator) in senses of point estimation and hypothesis testing via simulation studies. The results of estimation illustrate that regardless of the true values of RR, the MH estimator achieves the best performance with the smallest MSE when the study size is rather large and the sample sizes within each study are small. The MSE of WLS estimator and the proposed-weight estimator adjusted by , or , or are close together and they are the best when the sample sizes are moderate to large (and) while the study size is rather small.展开更多
It is well-known that the power of Cochran’s Q test to assess the presence of heterogeneity among treatment effects in a clinical meta-analysis is low due to the small number of studies combined. Two modified tests (...It is well-known that the power of Cochran’s Q test to assess the presence of heterogeneity among treatment effects in a clinical meta-analysis is low due to the small number of studies combined. Two modified tests (PL1, PL2) were proposed by replacing the profile maximum likelihood estimator (PMLE) into the variance formula of logarithm of risk ratio in the standard chi-square test statistic for testing the null common risk ratios across all k studies (i = 1, L, k). The simply naive test (SIM) as another comparative candidate has considerably arisen. The performance of tests in terms of type I error rate under the null hypothesis and power of test under the random effects hypothesis was done via a simulation plan with various combinations of significance levels, numbers of studies, sample sizes in treatment and control arms, and true risk ratios as effect sizes of interest. The results indicated that for moderate to large study sizes (k?≥ 16)?in combination with moderate to large sample sizes?(?≥ 50), three tests (PL1, PL2, and Q) could control type I error rates in almost all situations. Two proposed tests (PL1, PL2) performed best with the highest power when?k?≥ 16?and moderate sample sizes (= 50,100);this finding was very useful to make a recommendation to use them in practical situations. Meanwhile, the standard Q test performed best when?k?≥ 16 and large sample sizes (≥ 500). Moreover, no tests were reasonable for small sample sizes (≤ 10), regardless of study size k. The simply naive test (SIM) is recommended to be adopted with high performance when k = 4 in combination with (≥ 500).展开更多
In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal i...In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.展开更多
Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investnent.By the analysis of the conceptions of risk and return,together w...Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investnent.By the analysis of the conceptions of risk and return,together with the three hypotheses of technological analysis, a novelty model of metering and evaluating the risk and return of stock investnent is established.The major indicator of this model , risk-return ratio K, combines the characteristic indicators of risk and return. Regardless of the form of the risk-return probability density functions, this indicator K can always reflect the risk-return performances of the invested stocks clearly and accurately. How to use the model to make optimum investment and how to make portfolio combined with clustering analysis is also explained.展开更多
When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effecti...When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effectiveness of diagnostic and therapeutic devices and the risk-benefit ratio of patients, caregivers, and healthcare professionals. The guidelines evidence-based of large clinical data for this purpose are presented by national medical societies. As one of the rupture risk indicators, there is the hazard risk ratio derived by the UCAS Japan research group based on the statistical method of 6697 aneurysms in 5720 patients with cerebral aneurysms of 3 mm or more. Therefore, we investigated the biomechanical significance of this hazard risk ratio using a spherical aneurysm model. It was revealed that 1) the reason why the frequency of aneurysm rupture is relatively high up to about 10 mm, 2) the UCAS hazard risk ratio corresponds to stress of the aneurysm wall, and the true stress can be calculated by multiplying the patient’s blood pressure, and 3) the factors that cause the daughter’s sac (irregular protrusion of the aneurysm wall). In addition, our two methods for measuring the strength of the blood vessel wall of an individual patient were described.展开更多
Background: Maternal mortality is still high in sub-Saharan Africa, especially in Cameroon where more efforts to reduce maternal mortality and provide universal access to reproductive health should be made. This study...Background: Maternal mortality is still high in sub-Saharan Africa, especially in Cameroon where more efforts to reduce maternal mortality and provide universal access to reproductive health should be made. This study aims to see the evolution of maternal mortality and identify associated risk factors in Laquintinie hospital in Cameroon. Methods: A manual review of records for 166 maternal deaths (cases) and 322 controls was undertaken using a standard audit form. The sample included pregnant women aged 16 - 46 years admitted at the maternity of Laquintinie Hospital in Douala, Cameroon from January 2017 to December 2022. Software SSPS 3 and Logistic regression analysis were used to analyze data. Results: One hundred and sixty-six (166) maternal deaths were identified during the study period for 14,114 live births, representing a maternal mortality ratio of 1176/100,000 live births. Factors significantly associated with maternal mortality included: young age (15 - 24 years) (aOR 0.11, 95% CI 0.00 - 0.76, p = 0.037), Alcohol intake (aOR 22.79, 95% CI 1.04 - 501.3, p = 0.047), Abortion or ectopic pregnancy (aOR 61.53, 95% CI 1.29 - 2927.3, p = 0.037), having no antenatal visits (aOR 388.3 95% CI 5.6 - 2675.9, p = 0.006), being admitted with hemorrhage (aOR 343.7, 95% CI 16.2 - 7276.0, p ,713.0, 95% CI 128.2 - 5,989,223.3, p CI 0.00 - 0.18, p = 0.016). Conclusion: Despite slight decrease in maternal mortality, early diagnosis of pregnancy and good Antenatal care associated with maternal health education are important factors for reducing maternal mortality. Young women were the most affected. Singles, alcoholics, women with a no or only primary education level, and referred women represented the majority of deceased cases.展开更多
背景随着人口老龄化的加剧,心力衰竭(heart failure,HF)患病率呈上升趋势,老年心力衰竭的预警、风险分层研究对改善预后具有重要意义。目的探讨血尿素氮-白蛋白比值(blood urea nitrogen to albumin ratio,BAR)对老年心力衰竭患者1年内...背景随着人口老龄化的加剧,心力衰竭(heart failure,HF)患病率呈上升趋势,老年心力衰竭的预警、风险分层研究对改善预后具有重要意义。目的探讨血尿素氮-白蛋白比值(blood urea nitrogen to albumin ratio,BAR)对老年心力衰竭患者1年内死亡的预测价值;建立包含BAR在内的列线图,并验证其临床价值。方法建模数据来自解放军总医院2016年1月—2021年10月诊断为心力衰竭的1259例老年患者,验证队列来自2021年10月—2022年10月诊断为心力衰竭的314例老年患者。以1年病死率为结局指标,采用Logistic回归分析筛选预后因素,根据预后因素构建列线图;ROC曲线、校准曲线和临床决策曲线分析(decision curve analysis,DCA)用于评估模型的区分度、一致性和临床效益;通过计算ROC曲线下面积和DCA,比较列线图与N端脑钠肽前体(N-terminal pro-B-type natriureticpeptide,NT-proBNP)及BIOSTATCHF预测模型的性能。结果训练队列和验证队列中分别有27.2%(343/1259)和25.2%(79/314)患者在1年内死亡。多因素Logistic回归结果显示,年龄、D-二聚体、NT-proBNP、BAR、血管紧张素转化酶抑制剂(angiotensin converting enzyme inhibitor,ACEI)/血管紧张素受体阻滞剂(angiotensin receptor blockers,ARB)使用与死亡结局独立关联(P<0.05)。基于以上5个因素构建列线图,列线图展现出良好的区分度(AUC=0.838,P<0.001)、一致性(Hosmer-Lemeshowχ2=4.251,P=0.834)和临床效益。列线图模型与NT-proBNP和欧洲BIOSTAT-CHF预测模型相比预测效能均更佳(0.838 vs 0.703和0.825,P<0.05)。DCA结果提示,列线图相比NT-proBNP、BIOSTAT-CHF预测模型均增加了更多的净获益。结论BAR是老年心力衰竭患者1年内死亡的独立预测因子。包含BAR在内的列线图展现出优异的辨别力和校准能力,为预后评估提供有力支持。展开更多
文摘The paper aims to discuss three interesting issues of statistical inferences for a common risk ratio (RR) in sparse meta-analysis data. Firstly, the conventional log-risk ratio estimator encounters a number of problems when the number of events in the experimental or control group is zero in sparse data of a 2 × 2 table. The adjusted log-risk ratio estimator with the continuity correction points based upon the minimum Bayes risk with respect to the uniform prior density over (0, 1) and the Euclidean loss function is proposed. Secondly, the interest is to find the optimal weights of the pooled estimate that minimize the mean square error (MSE) of subject to the constraint on where , , . Finally, the performance of this minimum MSE weighted estimator adjusted with various values of points is investigated to compare with other popular estimators, such as the Mantel-Haenszel (MH) estimator and the weighted least squares (WLS) estimator (also equivalently known as the inverse-variance weighted estimator) in senses of point estimation and hypothesis testing via simulation studies. The results of estimation illustrate that regardless of the true values of RR, the MH estimator achieves the best performance with the smallest MSE when the study size is rather large and the sample sizes within each study are small. The MSE of WLS estimator and the proposed-weight estimator adjusted by , or , or are close together and they are the best when the sample sizes are moderate to large (and) while the study size is rather small.
文摘It is well-known that the power of Cochran’s Q test to assess the presence of heterogeneity among treatment effects in a clinical meta-analysis is low due to the small number of studies combined. Two modified tests (PL1, PL2) were proposed by replacing the profile maximum likelihood estimator (PMLE) into the variance formula of logarithm of risk ratio in the standard chi-square test statistic for testing the null common risk ratios across all k studies (i = 1, L, k). The simply naive test (SIM) as another comparative candidate has considerably arisen. The performance of tests in terms of type I error rate under the null hypothesis and power of test under the random effects hypothesis was done via a simulation plan with various combinations of significance levels, numbers of studies, sample sizes in treatment and control arms, and true risk ratios as effect sizes of interest. The results indicated that for moderate to large study sizes (k?≥ 16)?in combination with moderate to large sample sizes?(?≥ 50), three tests (PL1, PL2, and Q) could control type I error rates in almost all situations. Two proposed tests (PL1, PL2) performed best with the highest power when?k?≥ 16?and moderate sample sizes (= 50,100);this finding was very useful to make a recommendation to use them in practical situations. Meanwhile, the standard Q test performed best when?k?≥ 16 and large sample sizes (≥ 500). Moreover, no tests were reasonable for small sample sizes (≤ 10), regardless of study size k. The simply naive test (SIM) is recommended to be adopted with high performance when k = 4 in combination with (≥ 500).
文摘In this paper, we discuss the optimal insurance in the presence of background risk while the insured is ambiguity averse and there exists belief heterogeneity between the insured and the insurer. We give the optimal insurance contract when maxing the insured’s expected utility of his/her remaining wealth under the smooth ambiguity model and the heterogeneous belief form satisfying the MHR condition. We calculate the insurance premium by using generalized Wang’s premium and also introduce a series of stochastic orders proposed by [1] to describe the relationships among the insurable risk, background risk and ambiguity parameter. We obtain the deductible insurance is the optimal insurance while they meet specific dependence structures.
文摘Although widely used, both the Markowitz model and VAR (Value at Risk) model have some limitations in evaluating the risk and return of stock investnent.By the analysis of the conceptions of risk and return,together with the three hypotheses of technological analysis, a novelty model of metering and evaluating the risk and return of stock investnent is established.The major indicator of this model , risk-return ratio K, combines the characteristic indicators of risk and return. Regardless of the form of the risk-return probability density functions, this indicator K can always reflect the risk-return performances of the invested stocks clearly and accurately. How to use the model to make optimum investment and how to make portfolio combined with clustering analysis is also explained.
文摘When an unruptured aneurysm is found, deciding whether to operate or follow up is one of the most important issues. There are guidelines for making the best final decision on treatment, taking into account the effectiveness of diagnostic and therapeutic devices and the risk-benefit ratio of patients, caregivers, and healthcare professionals. The guidelines evidence-based of large clinical data for this purpose are presented by national medical societies. As one of the rupture risk indicators, there is the hazard risk ratio derived by the UCAS Japan research group based on the statistical method of 6697 aneurysms in 5720 patients with cerebral aneurysms of 3 mm or more. Therefore, we investigated the biomechanical significance of this hazard risk ratio using a spherical aneurysm model. It was revealed that 1) the reason why the frequency of aneurysm rupture is relatively high up to about 10 mm, 2) the UCAS hazard risk ratio corresponds to stress of the aneurysm wall, and the true stress can be calculated by multiplying the patient’s blood pressure, and 3) the factors that cause the daughter’s sac (irregular protrusion of the aneurysm wall). In addition, our two methods for measuring the strength of the blood vessel wall of an individual patient were described.
文摘Background: Maternal mortality is still high in sub-Saharan Africa, especially in Cameroon where more efforts to reduce maternal mortality and provide universal access to reproductive health should be made. This study aims to see the evolution of maternal mortality and identify associated risk factors in Laquintinie hospital in Cameroon. Methods: A manual review of records for 166 maternal deaths (cases) and 322 controls was undertaken using a standard audit form. The sample included pregnant women aged 16 - 46 years admitted at the maternity of Laquintinie Hospital in Douala, Cameroon from January 2017 to December 2022. Software SSPS 3 and Logistic regression analysis were used to analyze data. Results: One hundred and sixty-six (166) maternal deaths were identified during the study period for 14,114 live births, representing a maternal mortality ratio of 1176/100,000 live births. Factors significantly associated with maternal mortality included: young age (15 - 24 years) (aOR 0.11, 95% CI 0.00 - 0.76, p = 0.037), Alcohol intake (aOR 22.79, 95% CI 1.04 - 501.3, p = 0.047), Abortion or ectopic pregnancy (aOR 61.53, 95% CI 1.29 - 2927.3, p = 0.037), having no antenatal visits (aOR 388.3 95% CI 5.6 - 2675.9, p = 0.006), being admitted with hemorrhage (aOR 343.7, 95% CI 16.2 - 7276.0, p ,713.0, 95% CI 128.2 - 5,989,223.3, p CI 0.00 - 0.18, p = 0.016). Conclusion: Despite slight decrease in maternal mortality, early diagnosis of pregnancy and good Antenatal care associated with maternal health education are important factors for reducing maternal mortality. Young women were the most affected. Singles, alcoholics, women with a no or only primary education level, and referred women represented the majority of deceased cases.
