updateThetaUsingCombined is a function for updating '>examinee objects after completing a module.
updateThetaUsingCombined adds final theta estimates using all administered items in the test. A test may consist of multiple phases.
updateThetaUsingCombined(examinee_object, current_module_position, config)the current module position.
an '>examinee object with its estimated_theta_by_test slot updated.