Hydrogen content is conjectured to be an important factor in porosity of aluminum alloy castings. The article “The Reduced Pressure Test as a Measuring Tool in the Evaluation of Porosity/Hydrogen Content in A1–7 Wt Pct Si-10 Vol Pct SiC(p) Metal Matrix Composite” (Metallurg. Trans. 1993: 1857–1868) gives the accompanying data on x = content and y = gas porosity for one particular measurement technique.

Minitab gives the following output in response to a correlation command:
Correlation of Hydrcon and Porosity = 0.449
a. Test at level .05 to see whether the population correlation coefficient differs from 0.
b. If a simple linear regression analysis had been carried out, what percentage of observed variation in porosity could be attributed to the model relationship?

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