A researcher is interested in testing the popular belief that herbal remedies like Ginko Biloba and Ginseng may improve learning and memory. She obtains a sample of 16 participants. She has each...

A researcher is interested in testing the popular belief that herbal remedies like Ginko Biloba and Ginseng may improve learning and memory. She obtains a sample of 16 participants. She has each person take the herbal supplements every day for 90 days. At the end of the 90 days, each person takes a standardized memory test. For the general population, scores from the memory test form a normal distribution and they have a mean of 50 and a standard deviation of 12. The sample of the 16 research participants had an average memory score of 54.

What is the z-score that corresponds to the sample mean?