Final answer:
The patient's headache and feeling of nausea are subjective data, as they cannot be measured or observed by others but are reported by the patient. They are important in diagnosis and can sometimes be quantified through tools like the Wong-Baker scale or measuring skin conductance fluctuations.
Step-by-step explanation:
The symptoms described by the patient, a headache at the back of the head and feelings of nausea, are considered to be subjective data. Unlike objective signs that can be measured or observed directly, subjective symptoms are reported by the patient and cannot be independently confirmed by a clinician. Symptoms are an important aspect of diagnosis but are susceptible to individual variations in perception and reporting.
Clinicians may use tools such as the Wong-Baker Faces pain-rating scale to attempt to quantify subjective symptoms like pain by asking patients for a self-assessment that gives a numerical value. Another method involves the measurement of skin conductance fluctuations, which reflect the physiological response to pain.