The recommended dietary allowance (RDA) of iron for adult females under the age of 51 is 18 milligrams (mg) per day. The following iron intakes, in milligrams, were
obtained during a 24-hour period for 45 randomly selected adult females under the age
of 51.
15.0 18.1 14.4 14.6 10.9 18.1 18.2 18.3 15.0
16.0 12.6 16.6 20.7 19.8 11.6 12.8 15.6 11.0
15.3 9.4 19.5 18.3 14.5 16.6 11.5 16.4 12.5
14.6 11.9 12.5 18.6 13.1 12.1 10.7 17.3 12.4
17.0 6.3 16.8 12.5 16.3 14.7 12.7 16.3 11.5
At the 1% significance level, do the data suggest that adult females under the age of 51
are, on average, getting less than the RDA of 18 mg of iron? Assume that the population
standard deviation is 4.3 mg.