Sas enterprise guide 6.1 for windows

The values obtained for the four replicate measurements on Day 0 and Day 3 were averaged for each day and used to calculate the inter-day repeatability for the clinical scenario when using the mean value of measurements to assess progression of keratoconus. When calculating prediction limits in the clinical scenario when single measurements are used to assess progression, the variance between replicate measurements was included in the calculation to provide more accurate results.
IBM SPSS Statistics 22 Windows (IBM Corporation, Armonk, NY, USA) and SAS Enterprise Guide 6.1 for Windows (SAS Institute Inc., Cary, NC, USA) were used for statistical analyses. A p-value below 0.05 was considered significant. Descriptive statistics are given as subject mean, standard deviation (SD), and minimum and maximum values. Repeatability was assessed by calculating the within-subject standard deviation, precision, repeatability coefficient, intra-class correlation and coefficient of variation with associated confidence intervals (CIs)^{19 (link),20 (link),29 (link)}. Kendall’s tau was used to assess the relationship between the mean and SD, and natural logarithm transformed data were analysed when appropriate. The limits of agreement were calculated using the replicates and a linear mixed-effect model (denoted prediction limits)^{24 (link)}. A professional medical statistician was consulted.

IBM SPSS Statistics 22 for Windows (IBM Corporation, Armonk, NY, USA) and SAS Enterprise Guide 6.1 for Windows (SAS Institute Inc., Cary, NC, USA) were used for statistical analyses. Statistical significance was defined as a p-value of ≤ 0.05. Descriptive statistics are given as subject mean, standard deviation, median, and minimum and maximum values. Repeatability was assessed by calculating the within-subject standard deviation with 95% confidence intervals, the repeatability coefficient with 95% confidence intervals, intraclass correlation and the coefficient of variation [16 ] [17 ] [18 ]. Kendall’s Tau-b was used to analyse correlations between the mean and standard deviation of replicate measurements. Transformed (natural logarithm) data were analysed where appropriate. K1, K2 and Kmax values were divided into three groups based on parameter magnitude to give groups of as equal size as possible. Differences between coefficients of variation were assessed using a regression test [19 (link)]. Bland-Altman plots were used to analyse the agreement between the two instruments. Limits of agreement were calculated using a linear mixed model for replicate measurements [16 ]. A professional medical statistician was consulted.

IBM SPSS Statistics 22 for Windows (IBM Corporation, Armonk, NY, USA) and SAS Enterprise Guide 6.1 for Windows (SAS Institute Inc., Cary, NC, USA) were used for statistical analyses. A p-value below 0.05 was considered significant. Descriptive statistics are given as subject mean, standard deviation (SD), and minimum and maximum values. Repeatability was assessed by calculating the within-subject standard deviation (S_w), precision, repeatability coefficient, intra-class correlation (ICC) and coefficient of variation (CV%) with associated confidence intervals (CIs) [15 (link), 24 (link), 25 (link)]. Kendall’s Tau-b was used to assess the relationship between the mean and SD, and natural-logarithm-transformed data were analysed when appropriate. Differences between coefficients of variation were assessed using a regression test [26 (link)]. The Wilcoxon signed ranks test was used for comparisons of the means of the quality parameters on Day 0 and Day 3. A professional medical statistician was consulted and performed the analysis.