For a sample of 7 shirts, the thread count and life of the shirt (years) were recorded: Count 100 150 200 250 300 350 400 Life 1.

For a sample of 7 shirts, the thread count and life of the shirt (years) were recorded:

Count 100 150 200 250 300 350 400

Life 1.2 1.8 2.5 2.3 3.7 4.3 3.9

What percentage of the variation in a shirt's life is explained by the thread count?