The previous study (from 2 above) is criticised on the basis that the 13-millimetres average used is outdated. To silence critics, you decide to do a longitudinal study: you will measure the diameter of the substantiae nigrae of recently diagnosed psychotics, and compare them to the diameter after five years of having the disorder. This time, you make use of Magnetic Resonance Imaging (MRI) scans of patients to measure their substantiae nigrae. Fifteen patients diagnosed with psychosis less than one year ago agree to take part in the study. Your measurements are:
Measurement 1 13, 12, 16, 14, 13, 15, 17, 13, 14, 16, 13, 16, 13, 19, 12
After five years elapse, you contact as many of the patients as you can. Unfortunately, you are only able to contact nine of them. You measure again (NA means that patient was not available for a second measurement):
Measurement 2 9, 10, NA, NA, 10, NA, 11, 10, NA, 17, 9, 8, NA, 16,
NA Has there been a significant reduction in the size of the substantia nigra of these patients?