The FIFA (IRT) findings were similar to the results obtained from the factor analysis using tetrachoric correlation
, which supports the decision towards a unidimensional structure.
In correlation analysis of grains of hardwoods and images, the relationship between the grain and images was investigated using tetrachoric correlation
. The adjectives were treated as binary variables, and the grain characteristics of growth rings (clear/ring porous or unclear/diffuse porous), section (tangential or radial), and rays (thick or thin) were also treated as binary variables.
N = 4,539 patients at individual level of analysis,J= 223 clinics; standard deviation omitted for dichotomous variables tetrachoric correlations
reported between dichotomous variables; Spearman correlations reported between dichotomous and continuous variables; high correlation between HbAlc exam and control reflects the fact that scores require conducting tests.
From equation (1) it follows that, for a fixed item j, the sum of the tetrachoric correlations
with all of the test items is
Key words: statistical software; tetrachoric correlation
; approximation; point estimate; interval estimate.
By means of the R program the tetrachoric correlation
matrix was obtained, and we then checked whether a factorial analysis of the resulting questionnaire was applicable.
Notes: Reported figures are the factor loadings from the factor analysis of the tetrachoric correlation
matrix with pairwise deletion.
The explained relative variance is found by dividing the eigenvalues by the sum of the positive roots of the adjusted tetrachoric correlation
To explore the factorial structure of the e-MAPS, a single-level EFA was conducted based on the tetrachoric correlations
between the five e-MAPS items (Table 2).
were computed between two sets of scores for the whole sample; and for the two genders, and four age groups.
We analyzed the tetrachoric correlations
with the RWLS method, recommended for dichotomous items.
To address the concern that Pearson product-moment (PPM) correlations may not be appropriate, we also conducted the analysis on a matrix of poly- and tetrachoric correlations
and compared the results.