However, this condition can produce ambiguous
results that are associated with unstable estimated regression
coefficients and affects the calculations associated to individual
predictors. Instability in the estimated coefficients can be indicated
by large changes in the estimated regression coefficients
when a variable is added or deleted, or when a data point is
altered or dropped. When dealing with collinearity, the principal
component analysis (PCA) method is one of the most common
ways to reduce collinearity [25]. The PCA, contrary to grouping
methods such as cluster analysis, is a one-sample technique that
uses orthogonal transformation to obtain a set of values of linearly
uncorrelated variables called principal components, which can be
equal to or less than the original number of predictor variables.