二分类计数资料整群随机化样本量SAS宏实现

[目的]计算二分类计数资料整群随机化设计的组内相关系数及样本量。[方法]编写SAS宏程序,采用蒙特卡罗模拟方法,估计整群随机化设计的组内相关系数,并根据组内相关系数对样本量进行再计算。[结果]该宏程序可以方便地计算组内相关系数及样本量,并且通过利用SAS软件的ODS功能实现到word的输出。[结论]当组内相关系数未知而无法计算样本量时,该宏程序是可利用的方便工具。     

计量资料对应分析在SAS和SPSS软件中的实现

目的比较对应分析在SAS和SPSS软件中实现方法的异同,探讨在应用SAS软件进行对应分析时,计量资料原始数据应先进行标准化处理的必要性。方法使用SAS软件和SPSS软件,进行实例分析。结果计量资料对应分析在SPSS软件运行正常,但在SAS软件上应用时,因变量原始数据的不同量纲,导致SAS软件运行后出现相异或错误结果。结论 SAS软件只有在原始数据进行标准化处理后(有相同量纲或均无量纲),其进行对应分析的结果才最准确,而SPSS软件处理计量资料对应分析时可以不通过外部标化数据,直接输入原始数据。     

生存分析SAS和SPSS实现的比较

SAS和SPSS都能对生存资料进行较完善的生存分析，但它们所提供的生存分析过程不尽相同，过程下的选项和相应的输出结果也各有千秋，因此有必要对两个软件的生存分析功能做一个比较系统的比较，为实际工作者根据研究目的和所需计算结果选择恰当的统计分析软件提供依据。     

用统计软件计算肾小球系膜细胞对顺铂的半数抑制浓度

目的用SPSS和SAS程序计算小剂量激素诱导前后肾小球系膜细胞(HMC)对顺铂的IC50,进而计算耐药倍数。方法体外培养HMC,予小剂量(2μg/ml)甲基强的松龙刺激48h为耐药组,对照组常规培养,四甲基偶氮唑盐(MTT)法检测吸光度。应用SPSS和SAS程序计算IC50,计算经激素诱导后HMC对于顺铂的耐药倍数。结果 SPSS计算结果耐药倍数为5.388,SAS统计软件计算耐药倍数为5.382。结论 2种软件的计算结果比较接近且计算方便快捷,但SPSS计算更加快速、直观、方便。     

Mantel-Haenszel法在SPSS、SAS软件包中的实现

目的探讨分层分析法在SPSS、SAS软件包中的实现，以及如何解释分析结果。方法以实例介绍用SPSS15．0和SAS9．1实现分层分析。结果齐性检验）X2=0．044，P〉O．05，ORMH=1．35，ORMH95％可信区间=（1．15，1．59）。年龄为正混杂。结论SPSS、SAS软件均可进行分层分析。     

配对四格表资料χ2检验在 SPSS 和 SAS 软件中的实现

目的：通过实例来介绍配对四格表资料的卡方检验在SPSS和SAS统计分析软件中如何操作,输出结果的区别及正确的解读,为临床及相关科研人员提供可以借鉴的方法。方法使用SPSS和SAS统计软件,对配对四格表资料的卡方检验进行操作和分析。结果本文以两种方法诊断肺癌的检测结果为例题,根据基本公式算得统计量χ2＝4．92,P＜0．05,得出两种诊断方法的诊断结果存在差异。在SPSS软件的分析结果中只有P值,SAS软件的分析结果可以给出统计量和P的确切值,但统计量χ2＝6．23,与基本公式计算的结果不同,经过自编程序运行后,我们得到了与基本公式相同的结果。结论 SPSS和SAS统计软件是医学统计学数据分析的常用教学软件,本文通过实例详解,得出在结果的输出方面两种软件有很大区别,但这并不影响我们得出相同的统计结论。 SPSS软件操作简便,SAS软件编程比较麻烦,以及SAS软件在处理此类资料上存在默认不校正的问题,因此,在实际应用中,我们可以根据情况自行选择。     

诊断试验可靠性评价SAS程序实现

目的 用SAS程序实现诊断或筛检试验可靠性评价,从而简化运算过程,提高计算的准确度.方法 对Kappa指数和一致性相关系数的计算和假设检验过程编写SAS程序.结果将原始数据输入SAS程序中的相应数组后,运行程序便可很快得到可靠性评价的中间计算结果和最终结论.结论笔者编写的诊断试验或筛检试验可靠性评价SAS程序具有通用、简便、实用和易操作的特点,在实际评价工作中具有一定的实用价值.     

生长曲线偏度系数-中位数-变异系数法不同软件实现方法的比较

目的探讨不同软件对生长曲线偏度系数-中位数-变异系数(LMS)法的实现方法,优选适合基层使用的统计方法。方法使用包头市定期体检正常婴儿的3、6、9和12月龄头围数据,分别应用SAS、R、STATA和SPSS软件包进行生长曲线的LMS拟合,并从方便程度、难易程度、界面、结果展示及更新维护等4个方面对几种软件的使用效果进行评价。结果使用不同软件分别实现了生长曲线LMS的计算和绘图,绘制的包头市婴儿的头围生长曲线的各百分位数值结果一致。从操作步骤、难易程度、操作界面、操作选项、更新维护、软件成本和结果展示来看,R软件更具优势。结论在常用生长曲线LMS的计算和绘图方面,与SAS、STATA和SPSS软件相比,R软件综合了各软件的优点,比较适于基层妇幼保健工作者使用。     

不等距重复测量设计方差分析用SAS和SPSS实现的对比

目的探讨不等距重复测量设计方差分析的条件及结果解释。方法用SAS和SPSS软件实现不等距重复测量设计方差分析。结果给出了方差分析条件、SAS和SPSS程序及主要结果解释。结论只有满足方差分析条件、正确合理解释结果,才能保证不等距重复测量设计方差分析的有效性。     

四格表资料非条件精确检验的SAS实现

目的 探索四格表资料非条件精确检验的软件实现.方法 使用SAS软件,借助于SAS宏语句编制相关程序.结果 通过实例验证,本程序得出的结果是正确可靠的,同时其运算速度也是较为快捷的.结论 本程序可以作为SAS软件四格表资料统计分析模块的补充,经过修改和拓展之后,还可以实现更多类型资料的精确检验.     

Kappa coefficients in medical research

Kappa coefficients are measures of correlation between categorical variables often used as reliability or validity coefficients. We recapitulate development and definitions of the K (categories) by M (ratings) kappas (K x M), discuss what they are well- or ill-designed to do, and summarize where kappas now stand with regard to their application in medical research. The 2 x M(M>/=2) intraclass kappa seems the ideal measure of binary reliability; a 2 x 2 weighted kappa is an excellent choice, though not a unique one, as a validity measure. For both the intraclass and weighted kappas, we address continuing problems with kappas. There are serious problems with using the K x M intraclass (K>2) or the various K x M weighted kappas for K>2 or M>2 in any context, either because they convey incomplete and possibly misleading information, or because other approaches are preferable to their use. We illustrate the use of the recommended kappas with applications in medical research.     

Comparison of Rolyan and Jamar dynamometers for measuring grip strength

This study compared the Jamar and Rolyan hydraulic dynamometers to determine their concurrent validity with known weights as well as their inter-instrument reliability and concurrent validity for measuring grip strength in a clinical setting. Thirty females and 30 males were tested on these two grip strength measurement devices using a repeated measure design. Results showed that the Jamar and Rolyan dynamometers have acceptable concurrent validity with known weights (that is, correlation coefficients were r > or = 0.9994), excellent inter-instrument reliability (that is, intraclass correlation coefficients ranged from 0.90 to 0.97) and strong concurrent validity (that is, no significant differences between dynamometers' scores). Data indicate that Jamar and Rolyan dynamometers measure grip strength equivalently and can be used interchangeably. Thus, therapists using the Rolyan dynamometer are justified in using published normative data, which were collected with the Jamar dynamometer.     

Reliability and sensitivity to change assessed for a summary measure of lower body function: results from the Women's Health and Aging Study

A summary performance measure comprised of a hierarchical balance task, a 4-meter walk, and five repetitive chair stands is increasingly being used as a predictor of independent living for older persons. The reliability and sensitivity to change of this summary performance measure have not been investigated, however. Because a measure can be reliable while being unresponsive to change, this study presents information on both the reliability and sensitivity to change for the summary performance measure. This is a 3-year prospective cohort study of 1,002 moderately to severely disabled older women. Short- and long-term reliability was assessed by intraclass correlation coefficients (ICC). Sensitivity to change was assessed by slope differences for three age categories (65-74, 75-84, and >or=85) over six 6-month follow-up periods. Sensitivity to change was also assessed by summary performance change scores for those who did and did not suffer from one of four medical events [myocardial infarction (MI), stroke, hip fracture, or congestive heart failure (CHF)] at follow-up. The summary performance measure showed excellent reliability. Intraclass correlation coefficients ranged from 0.88 to 0.92 for measures made 1 week apart. The 6-month average intraclass correlation coefficient was 0.77 (range 0.72-0.79). The summary performance measure was also highly responsive to change. Subjects who suffered an incident MI, stroke, hip fracture, or CHF at follow-up were significantly more likely to have poorer summary performance change scores (-2.25) compared with those who did not have one of these medical events (-0.24). Additionally, subjects who suffered one of these events improved their summary performance scores in the following assessment period by 0.72. With increasing utilization of the summary performance measure by researchers and clinicians it is important that the measurement properties of this instrument are known. Our results show that the summary performance measure has excellent reliability and is highly sensitive to change.     

Intraclass correlation coefficients and bootstrap methods of hierarchical binary outcomes

Intraclass correlation coefficients are designed to assess consistency or conformity between two or more quantitative measurements. When multistage cluster sampling is implemented, no methods are readily available to estimate intraclass correlations of binomial-distributed outcomes within a cluster. Because statistical distribution of the intraclass correlation coefficients could be complicated or unspecified, we propose using a bootstrap method to estimate the standard error and confidence interval within the framework of a multilevel generalized linear model. We compared the results derived from a parametric bootstrap method with those from a non-parametric bootstrap method and found that the non-parametric method is more robust. For non-parametric bootstrap sampling, we showed that the effectiveness of sampling on the highest level is greater than that on lower levels; to illustrate the effectiveness, we analyse survey data in China and do simulation studies.     

The development of a scale to measure medical students' attitudes towards communication skills learning: the Communication Skills Attitude Scale (CSAS)

INTRODUCTION: There is little research identifying medical students' attitudes towards communication skills learning. This pilot study outlines the development of a new scale to measure attitudes towards communication skills learning. METHODS: First- and second-year medical students (n = 490) completed the 26-item Communication Skills Attitude Scale (CSAS) and 39 students completed the CSAS on a second occasion. Factor analysis was conducted to determine the factors underpinning the scale. The internal consistency of the subscales was determined using alpha coefficients. The test-retest reliability of the individual scale items were determined using weighted kappa coefficients and the test-retest reliability of the subscales were established using intraclass correlation coefficients. RESULTS: Maximum likelihood extraction with direct oblimin rotation resulted in a 2-factor scale with 13 items on each subscale. Factor I represented positive attitudes towards communication skills learning and factor II represented negative attitudes. Subscale I had an internal consistency of alpha=0.873 and an intraclass correlation of 0.646 (P < 0.001). Subscale II had an internal consistency of alpha=0.805 and an intraclass correlation of 0.771 (P < 0.001). The majority of items on the positive (n=9, 69.2%) and the negative attitude subscales (n=8, 61.5%) possessed moderate test-retest reliability. DISCUSSION: The development of a new and reliable scale to identify medical students' attitudes towards communication skills learning will enable researchers to explore the relationships between medical students' attitudes and their demographic and education-related characteristics. Further work is needed to validate this scale among a broader population of medical students.     

A note on the effect of the intraclass correlation in the multiple reading procedure with a unanimity rule.

The use of multiple reading procedures to improve the performance of a diagnostic test occurs often in practice. Evaluation of the utility of multiple reading procedures, however, usually ignores the effect of the intraclass correlation. This paper provides a quantitative assessment of this effect in the multiple reading procedure with a unanimity rule with respect to sensitivity, specificity, positive and negative predictive values. We have found that when the disease prevalence is rare or moderate (less than or equal to 0.20), use of the multiple reading procedure with a unanimity rule is effective in increasing the positive predictive value of a single reading procedure for the situation in which the variation of responses among different subjects and the intraclass correlation among repeated tests are small. This is, however, not true for the situation in which the disease is rare and the variation of responses among different subjects is large, even when the intraclass correlation is small or 0. Furthermore, when the disease is rare and the variation of responses among subjects is small, a small or moderate intraclass correlation can substantially decrease the positive predictive value that one calculates under the assumption that the intraclass correlation is equal to 0. In general, when the disease is rare or moderate (less than or equal to 0.20), the intraclass correlation between repeated tests and the variation of responses among subjects have little effect on the negative predictive value.     

Interobserver reliability of radiologists' interpretations of mobile chest radiographs for nursing home-acquired pneumonia

OBJECTIVES: To determine the interobserver reliability of radiologists' interpretations of mobile chest radiographs for nursing home-acquired pneumonia. DESIGN: A cross-sectional reliability study. SETTING: Nursing homes and an acute care hospital. PARTICIPANTS: Four radiologists reviewed 40 mobile chest radiographs obtained from residents of nursing homes who met a clinical definition of lower respiratory tract infections. MEASUREMENTS: Radiologists were asked to interpret radiographs with respect to the film quality; presence, pattern, and extent of an infiltrate; and the presence of a pleural effusion or adenopathy. Interrater reliability was evaluated using the intraclass correlation coefficient derived from a 2-way random effects model. RESULTS: On average the radiologists reported that 6 of the 40 films were of very good or excellent quality and 16 of the 40 were of fair or poor quality. When the finding of an infiltrate was dichotomized (0 = no; 1 = possible, probable, or definite) all 4 radiologists agreed on 21 of the 37 chest radiographs. The intraclass correlation coefficient for the presence or absence of infiltrates was 0.54 (95% confidence intervals [CI] 0.38 to 0.69). For the 14 radiographs where infiltrates were observed by all radiologists, intraclass correlation coefficients for the presence of pleural effusions was 0.08 (95% CI -0.10 to 0.41), hilar adenopathy 0.54 (95% CI 0.29 to 0.79), and mediastinal adenopathy 0.49 (95% CI 0.21 to 0.76). CONCLUSION: In conclusion, the interrater agreement among radiologists for mobile chest radiographs in establishing the presence or absence of an infiltrate can be judged to be "fair." Treatment decisions need to include clinical findings and should not be made based on radiographic findings alone.     

Best reproducibility of the ankle-arm index was calculated using Doppler and dividing highest ankle pressure by highest arm pressure

BACKGROUND AND OBJECTIVE: To investigate which method of ankle-arm index (AAI) measurement in terms of selected arteries and blood pressure devices yields the highest reproducibility. STUDY DESIGN AND SETTING: In this cross-sectional study, duplicate AAI measurements were obtained at the right and left side in 320 postmenopausal women. Analyses were done as proposed by Bland and Altman and intraclass correlation coefficients were calculated. RESULTS: The mean and standard deviation (SD) of the first and second systolic blood pressure (SBP) measurement separately did not differ from the mean and SD of the duplicate SBP measurements averaged. Coefficients of repeatability and intraclass correlation coefficients were comparable when the ankle SBP was measured in the posterior tibial artery or dorsalis pedis artery. Coefficients of repeatability as well as the intraclass correlation were better when the SBP in the brachial artery was measured with Doppler than with Dinamap. CONCLUSIONS: To achieve the best reproducibility and smallest systematic difference in the AAI, single SBP measurements should be obtained by Doppler in the brachial artery, posterior tibial artery and dorsalis pedis artery. The AAI should be calculated for each foot separately by dividing the highest ankle SBP by the highest arm SBP.     

Validation and calibration of mercury intake through self-referred fish consumption in riverine populations in Pantanal Mato-grossense, Brazil

The objective of most epidemiological studies is to classify/rank people according to their relative quantity of consumption. In the specific case of quantifying fish consumption, in order to assess mercury intake rate, the method used must estimate the individual quantity consumed accurately, or from the self-referred quantity it must be possible to estimate the real consumption-termed calibration. Therefore, the objective of this study was to validate and calibrate the 24-h recall method for assessing the amount of fish consumed to estimate the mercury intake in riverine populations from Baixada Cuiabana, in Pantanal Mato-grossense, Brazil. The weighed dietary method was used as the reference standard, and the validity of the 24-h recall method was assessed using correlation coefficients (r), regression coefficients (beta), and the intraclass correlation coefficient (ICC). The results showed that the ICC, which assesses the agreement level between measures, was a more adequate measure than the correlation coefficient (r). Therefore, the calibration equation was calculated applying a multiple linear regression model using the consumption mean of the second and third days, which presented the highest ICC, stratified by sex and adjusted by age and season variables.     

Intraclass correlation coefficients from three cluster randomised controlled trials in primary and residential health care

OBJECTIVE: This paper provides intraclass correlation coefficients (ICCs) for estimation of sample size inflation required in future cluster randomised trials in primary or residential care. METHODS: Three cluster randomised trials were conducted among middle-aged and older adults in primary care and residential care in Australia and New Zealand between 1995 and 2002. Baseline means or proportions, mean change, and ICCs with their standard errors and 95% confidence intervals are reported for outcome variables used in the three studies. The ICCs were estimated from a one-way random effects model using the analysis of variance method. RESULTS: ICCs for quality of life and psychological variables in the primary care studies were low (below 0.018). ICCs for clinical and physical activity variables ranged from 0 to 0.08. ICCs for health and functional status in residential care for the elderly were high, ranging from 0.025 to 0.514. CONCLUSIONS: The magnitude of the intraclass correlation varies with the venue of the trial, the outcome variables used, and the expected effect of the intervention. However, the intraclass correlations provided will be useful for more appropriate planning of residential and primary care-based trials in the future.