The Incorporation of Uranium and Silver by Hydrothermally Synthesized Galena" (Econ. Geology, 1964: 1003-1024) reports on the determination of silver content of galena crystals grown in a closed hydrothermal system over a range of temperature. With x = crystallization temperature in ?C and y = Ag2S in mol%, the data follows:

a. Estimate true average silver content when temperature is 500?C using a 95% confidence interval.

b. How would the width of a 95% CI for true average silver content when temperature is 400?C compare to the width of the interval in part (a)? Answer without computing this new interval.

c. Calculate a 95% CI for the true average change in silver content associated with a 1?C increase in temperature.

d. Suppose it had previously been believed that when crystallization temperature was 400?C, true average silver content would be. 25. Carry out a test at significance level .05 to decide whether the sample data contradicts this prior belief.

x 398 292 352 575 568 450 550 408 484 350 503 600 600 y .15 .05 .23 43 23 .40.44.44.45 .09 59 63.60 from which xi = 6130, x2i = 3,022,050, yj = 4.73, y2i = 2.1785, yj = 2418.74, . = .00143, = .311, and s = .131.