Measuring the Mass of Ore Samples

Suppose 100 geology students measure the mass of an ore sample. Due to human error and limitations in the reliability of the balance, not all the readings are equal. The results are found to closely approximate a normal curve, with mean 75 g and a standard deviation 2 g.

Use the symmetry of the normal curve and the empirical rule to estimate the number of students reporting readings in the following ranges.

(a) more than 75g

(b) more than 73g

(c) between 71 and 79g

(d) between 69 and 77g