As demonstrated, the lower quartiles of correlation coefficients Q1CT and Q1TN could imply the "least spectral similarity" between different tissue types.
Because preliminary analyses indicated that benzene and 1,3-butadiene levels (broken down by quartiles) were highly correlated (Spearman correlation coefficient = 0.91, p < 0.0001), we were unable to include these two variables in the same regression model because of issues associated with collinearity.
For this estimate, we defined high-level arsenic exposure as levels within the top quartile of observed; we assumed a correlation coefficient between cases and controls of 0.2 and a Type I error of 0.05.
The reproducibility between the first and second FFQ administrations was estimated using the Wilcoxon signed rank test, intraclass correlation coefficient (ICC), weighted kappa statistic, and misclassification (quartiles method) analyses [14].
*Inter Quartile Range The correlation between perceived stress and academic performance was assessed using Pearson correlation coefficient; this was negative and not significant (r = -0.099, p > 0.05).
Trend effects according to the number of vessels diseased or over the quartiles of Gensini and Sullivan scores were estimated by Spearman's rank-order correlation coefficient for continuous values and the chi-squared test for trend for categorical data.
Correlation of PD between image representations (n = 360) was evaluated using Pearson's correlation coefficient (r) on the continuous measures and the weighted kappa statistic for quartiles.
Similar effects were confirmed for methadone: an inverse correlation was found between quartiles of average daily methadone doses with urine samples tested positive for 6-MAM (Pearson's correlation coefficient −0.2225; P = 0.0051) and 6-A-cod (Pearson's correlation coefficient: −0.1868; P = 0.0192).
The MRIpercentt dense volume estimates were highly consistent between the two readers for the 97 images read by both, with a correlation coefficient of 0.94 and a weighted inter-reader kappa of 0.74 based on the quartiles.
The correlation coefficient, r, measures the extent of the correlation between two variables.
