Exercise
Weight Loss of Coins

Suppose you have to solve the following problem. Some department of the mint wants to know whether their coins lose weight during usage over the years. They have therefore collected 114 coins of the same kind, but of different minting date, spanning a range of three decades. All of the coins are washed, dried, and weighted thereafter. The results are stored in file COINS.

Your task is now
 

• to decide if the weight of the coins decreases over time, and if so,
• to give an estimate of the weight loss per year.
• to compare the variance to the weight change?
• Is the variance homoscedastic or heteroscedastic?

Go to the  DataLab  to investigate these questions.