Homework Page 240 #8, 9, 11, 12 Step-by-Step Example Standard fishing line comes in a range of strengths, usually expressed “test as pounds.” Five-pound test lines, for example, can be expected to withstand a pull of up to five pounds without breaking. The convention in selling fishing line is that the price of a spool doesn’t vary with strength. Higher test pound line is thicker, though, so spools of fishing line hold about the same amount of material. Let’s look at Length and Strength of spools of fishing line manufactured by the same company and sold for the same price at one store. Question How are the Length on the spool and the Strength related? And what re-expression will straighten the relationship? THINK I want to fit a linear model for the length and strength of fishing line. I have the length and “pound test” strength of fishing line sold by a single vendor at a particular store. Let Length = length in yards of fishing line on the spool Strength = the test strength in pounds The plot shows a negative direction and an association that has little scatter but is not straight. SHOW Let’s try a re-expression of the data to make it more nearly linear. Below is a scatterplot of the square root of Length against the strength: The plot is less bent, but not straight.
Homework Page 240 #8, 9, 11, 12 Step-by-Step Example Standard fishing line comes in a range of strengths, usually expressed as “test pounds.” Five-pound test lines, for example, can be expected to withstand a pull of up to five pounds without breaking. The convention in selling fishing line is that the price of a spool doesn’t vary with strength. Higher test pound line is thicker, though, so spools of fishing line hold about the same amount of material. Let’s look at Length and Strength of spools of fishing line manufactured by the same company and sold for the same price at one store. Question How are the Length on the spool and the Strength related? And what re-expression will straighten the relationship? THINK I want to fit a linear model for the length and strength of fishing line. I have the length and “pound test” strength of fishing line sold by a single vendor at a particular store. Let Length = length in yards of fishing line on the spool Strength = the test strength in pounds The plot shows a negative direction and an association that has little scatter but is not straight. SHOW Let’s try a re-expression of the data to make it more nearly linear. Below is a scatterplot of the square root of Length against the strength: The plot is less bent, but not straight.