Expand Your Knowledge: Logarithmic Transformations, Power Law Model Let x= boiler steam pressure in 100 lb/in.2 and let y= critical sheer strength of boiler plate steel joints in tons/in.2. We have the following data for a series of factory boilers.
x | 4 | 5 | 6 | 8 | 10 |
y | 3.4 | 4.2 | 6.3 | 10.9 | 13.3 |
(a) Make the logarithmic transformations x’ = log xand y’ = log y. Thenmake a scatter plot of the (x’, y’)values. Does a linear equation seem to be a good fit to this plot?
(b) Use the (x’, y’) data points and a calculator with regression keys to find the least-squares equation y’ = a + bxoe. What is the sample correlation coefficient?
(c) Use the results of part (b) to find estimates for a and b in the power law y = axb. Write the power equation for the relationship between steam pressure and sheer strength of boiler plate steel.
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