Spearman correlation coefficient

On occasion you need to obtain correlation coefficients between two variables. Correlation coefficients are a way of measuring linear relationships between two variables. A correlation coefficient of 1 or -1 indicates a perfect linear relationship, and a coefficient of 0 indicates no strong linear relationship. Pearson correlation coefficients are useful for continuous variables, while Spearman correlation coefficients are useful for ordinal variables. For example, look at the following SAS code ... 

The first PROC CORR sends the Pearson correlation coefficients to a data set called pearson for the continuous variables Age and Weight, while the second PROC CORR sends the Spearman correlation coefficients to a data set called spearman for the categorical variables Race and Treatment Success. The correlation coefficients are found where the TYPE variable is equal to CORR in the pearson and spearman data sets. 

The Spearman correlation coefficient works in essentially the same way as Pearson s. Its value can be anything between —1 and +1. Zero represents no correlation and the extreme values either perfect negative or perfect positive correlation. In this case, a Spearman correlation coefficient of +0.748 indicates quite a strong relationship. The P value is strongly significant, so it looks as if we were wasting our money when we hired the consultant (how unusual is that ). 

Obviously, the values of the estimated Spearman correlation coefficients equal nearly 0. That means that there are no detectable interdependences between the important dental drill characteristics. This leads also to non-depending tolerances zones. This is one precondition for the presented method of MPCI regarding the analysed multidimensional tolerance area. 

Spearman correlation coefficient showed that there was positive significant correlation between gait velocity and estimated variables in stance phase of walking. For quasistiffness r=0.901 and p= 0.006, for hysteresis r= 0.929 and p= 0.003 and for power r=0.893 and p=0.007 were found. 

Data are presented as mean SD. Data were tested for normal distribution. Multiple group comparison was carried out using ANOVA or Kruskal-Wallis test, with post-hoc Scheffe s test, or Mann-Whitney U test, where appropriate. Pearson or Spearman correlation coefficients were calculated, as appropriate. General linear model was employed to study the impact of independent variables on skin autofluorescence levels. P<0.05 was considered significant. Statistical program SPSS 16 was used. 

Table 5 Spearman correlation coefficients for PbB at different ages (rf Age Birth 6 months 12 months 18 months 24 months...

Table 3. Correlation between plasnui cotinine and lipoprotein fractions in men (Spearman correlation coefficients)...

The mechanistic simulation ACAT model was modified to account automatically for the change in small intestinal and colon k as a function of the local (pH-dependent) log D of the drug molecule. The rank order of %HIA from GastroPlus was directly compared with rank order experimental %HIA with this correction for the log D of each molecule in each of the pH environments of the small intestine. A significant Spearman rank correlation coefficient for the mechanistic simulation-based method of 0.58 (p < 0.001) was found. The mechanistic simulation produced 71% of %HIA predictions within 25% of the experimental values. 

Fischer (30) reported that airborne respirable endotoxin levels correlate (Spearman s coefficient of rank correlation) with the counts of gram-negative rods, with the percent of the total material processed that is Memphis cotton, and with the decrease in FEV, if these data are calculated only on mills where the carding areas are separate from the spinning areas. 

Fields can be utilized in virtual screening applications for assessing the similarity (alignment) or complementarity (docking) of molecules. Two similarity measures have achieved the most attention. These are the so-called Garbo- [195] and Hodgkin indexes [196] respectively. Others are Pearson s product moment correlation coefficient [169] and Spearman s rank correlation coefficient [169]. 

Trace element contents in rocks intersected by drill holes WB-08-03 to WB-08-06 are associated with altered rhyolite Spearman rank correlation coefficients for Ag, Mo and S with Au are moderate to high. Correlation coefficients for Au with As, Cu, Sb and Mo in drill hole WB08-11 (vuggy quartz) are moderate to high. These element correlations suggest that mineralization may be related to an epithermal system (Panteleyev 1995). 

For each IC50 bin, the percentage of compounds that list the ADR was calculated as percent ADR positive. For each group of seven IC50 bins, a Spearman rank correlation coefficient was calculated for the percent ADR positive relative to the bin rank. A strong Spearman correlation indicates a dose response in the ADR association. 

III.2. Comparison with Spearman s Rank Correlation Coefficient... 

Apparently the oldest nonparametric measure of the strength of association between two factors [26], the Spearman rank correlation coefficient... 

In an alternative approach, critical values of Spearman s rank correlation coefficient, tabulated as a function of observation size and significance probability [32], are employed. The 5% critical value is 0.738 when N = 8, hence rs = 0.369 is not significant (not even at the 10% level, with critical value 0.643). 

While the Youden plot (Figure 3) indicates that there is systematic error in the various laboratories, a test by Spearmans rank correlation coefficient (Table Vb) is ambiguous. The ranking is significant at the 0.05 level but not at the 0.01 level thus a correlation of the ranks of the laboratories such as we see here would appear less than five times in 100 by chance but more than one time in 100. I prefer to look at these results in terms... 

As above represented it is necessary to test the ruggedness of FA against deviations from the normal distribution FA was, therefore, conducted on the basis of the SPEARMAN rank correlation coefficient [WEBER, 1986]. The obtained factor loading matrix... 

Several authors used the Spearman rank correlation coefficient as a MEP-SI in similarity investigations [112, 114, 115] ... 

If normality of the data cannot be accepted, Spearman s correlation coefficient and its corresponding nonparametric test can be used for the null hypothesis Ho =... 

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