The distribution of the amount of money spent by students on textbooks in a semester is approximately normal in shape with a mea
n of: μ = 473 and a standard deviation of: σ = 28. According to the standard deviation rule, almost 0.15% of the students spent more than what amount of money on textbooks in a semester?
As distribution is normal in shape and values are symmetrical
The standard deviation rule says that 95% of observation lies between the second standard deviation of the mean
so, approximately only 5% of observation lies outside the interval and normal shape is symmetric. hence approximately 0.15% of observation lies above the interval