Answer
a. Yes, there is a change in the weight of pennies during the year 1982
$\text{}$
b. There are too many significant figures, it should be expressed as 3.08 ± 0.05 g
Work Step by Step
a. All of the light pennies were minted in 1982 or 1983. In contrast, all of the heavier pennies were minted between 1970 and 1982. Thus, the change in mass indicates that there was a change in the metal composition of pennies minted that year.
$\text{}$
b. Uncertainty should always be rounded to only one significant figure unless the rounded digit would be ≤ 3 in which case two significant figures are retained. In this case, the uncertainty of the average is 0.0482 which should be rounded to one significant figure 0.05 since 5 > 3. Consequently the actual value must also be rounded to the same decimal place.
