13. The accompanying data on x
current density (mA/cm2

)

and y
rate of deposition (m/min) appeared in the article

“Plating of 60/40 Tin/Lead Solder for Head Termination Metallurgy” (Plating and Surface Finishing, Jan. 1997:

38–40). Do you agree with the claim by the article’s author that “a linear relationship was obtained from the tin-lead rate of deposition as a function of current density”? Explain your reasoning.

14. Refer to the tank temperature–efficiency ratio data given in Exercise 1.

a. Determine the equation of the estimated regression line.

b. Calculate a point estimate for true average efficiency ratio when tank temperature is 182.

c. Calculate the values of the residuals from the least squares line for the four observations for which temperature is 182. Why do they not all have the same sign?

d. What proportion of the observed variation in efficiency ratio can be attributed to the simple linear regression relationship between the two variables?