In a bone density test, one of the results is given as a z-score. This is simply the number of standard deviations above or below the average bone density of someone of the same sex and age as the patient. For a certain age and sex, the bone density scores are thought to be normally distributed in the population. One of the authors had a bone density test and received a z-score of −0.3. 

a. What percentage of the population (in this case, 56-year-old males) has bone density smaller than that of the author? 

b. In what percentile does this score place the author?