60. 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 (Metallurgical Trans., 1993:

1857—1868) gives the accompanying data on x 

content and y gas porosity for one particular measurement technique.

x .18 .20 .21 .21 .21 .22 .23 y .46 .70 .41 .45 .55 .44 .24 x .23 .24 .24 .25 .28 .30 .37 y .47 .22 .80 .88 .70 .72 .75 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 coef cient 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?