If a decline of 2% in bone-mineral density is considered clinically significant, then what percentage of women in the placebo group can be expected to show a decline of at least this much? 

Endocrinology

A study compared different treatments for preventing bone loss among postmenopausal women younger than 60 years of age [6]. The mean change in bone-mineral density of the lumbar spine over a 2-year period for women in the placebo group was −1.8% (a mean decrease), with a standard deviation of 4.3%. Assume the change in bone-mineral density is normally distributed.