Figure 1
The horizontal axis is labeled “Theta (Trait Level)” and ranges from negative 4 to positive 4 in increments of 2 units. The vertical axis is labeled “Value” and ranges from 2 to 6 in increments of 2 units. A legend titled “Key:” is positioned at the top center, showing two curve types: a red dashed line labeled “Standard Error S E (theta)” and a solid blue line labeled “Test Information I (theta)”. The solid blue curve begins near (negative 4, 1), rises steadily with an increasing positive slope in a concave-down manner, reaches its peak at approximately (0.29, 7.56), and then declines in a concave-down shape with a decreasing slope, ending at (4, 1.47). The red dashed curve starts at (negative 4, 1), dips slightly downward to its lowest point around (0, 0.42), and then rises again toward (3.9, 0.86), forming a shallow U-shape. Note: All numerical data values are approximated.Test information function of the scale