Studies suggest that Parkinson’s disease (PD) affects nerve endings in the heart that produce the chemical norepinephrine. Low levels of norepinephrine decrease the patient’s ability to control muscle...

Studies suggest that Parkinson’s disease (PD) affects nerve endings in the heart that produce the chemical norepinephrine. Low levels of norepinephrine decrease the patient’s ability to control muscle movement, hence producing the shaking symptoms associated with PD. A random sample of women with PD was obtained, and the concentration of norepinephrine (in nmol/L) was measured in each. The data are given in the following table.