Chapter 5.12, Problem 30E

A concern to public health officials is whether a concentration of lead in the paint of older homes may have an effect on the muscular development of young children. In order to evaluate this phenomenon, a researcher exposed 90 newly born mice to paint containing a specified amount of lead. The number of Type 2 fibers in the skeletal muscle was determined 6 weeks after exposure. The mean number of Type 2 fibers in the skeletal muscles of normal mice of this age is 21.7. The n = 90 mice yielded $\bar{y}$ = 18.8, s = 15.3. Is there significant evidence in the data to support the hypothesis that the mean number of Type 2 fibers is different from 21.7 using an α = .05 test?