Figure 2. Path diagram for The University of Iowa operating room suite. The path diagram represents the system of simultaneous linear statistical equations or "structural Equation model." The seven observed variables are represented by the rectangular boxes. All terms in the Figure aredefined in the Methods section "Generating the Covariance Matrix." The variances of the random effect terms are given within the circles. The size of the circle is an indication of the variance. Each of the numbers written next to an arrow corresponds to a coefficient in Equation 1, Equation 2, Equation 3, Equation 4, Equation 5. The width of the line is an indication of the magnitude of the coefficient. These are referred to as "un-standardized" regression coefficients in the statistical literature. For example, the value 1.4 between "elective estimated" and "elective" implies that each increase of 1 h in the estimated hours of elective cases causes an increase of 1.4 h in actual hours of elective cases.