Chapter 1, Problem 112CP

A person weighed 15 pennies on a balance and recorded the following masses:

3.112 g	3.109 g	3.059 g
2.467 g	3.079 g	2.518 g
3.129 g	2.545 g	3.050 g
3.053 g	3.054 g	3.072 g
3.081 g	3.131 g	3.064 g

Curious about the results, he looked at the dates on each penny. Two of the light pennies were minted in 1983 and one in 1982. The dates on the 12 heavier pennies ranged from 1970 to 1982. Two of the 12 heavier pennies were minted in 1982.

1. a. Do you think the Bureau of the Mint changed the way it made pennies? Explain.
2. b. The person calculated the average mass of the 12 heavy pennies. He expressed this average as 3.0828 g ± 0.0482 g. What is wrong with the numbers in this result, and how should the value be expressed?