Question 6.46
11. Use spreadsheet software or a graphing calculator for this exercise. (Spotlight 6.1 on page 249 provides instruction for TI-83/84 graphing calculators and Excel.) The presence of mercury in fish is a health hazard, particularly for women who may become pregnant and children. Table 6.8 contains data on mercury concentration in tissue samples from 20 largemouth bass taken from Lake Natoma (California). Only fish of legal/edible size were used in this study. (Save your data and work from this exercise for use in Exercise 31.)
280
| Total Length, (mm) | Mercury Concentration, ( wet wt.) |
|---|---|
| 341 | 0.515 |
| 353 | 0.268 |
| 387 | 0.450 |
| 375 | 0.516 |
| 389 | 0.342 |
| 395 | 0.495 |
| 407 | 0.604 |
| 415 | 0.695 |
| 425 | 0.577 |
| 446 | 0.692 |
| 490 | 0.807 |
| 315 | 0.320 |
| 360 | 0.332 |
| 385 | 0.584 |
| 390 | 0.580 |
| 410 | 0.722 |
| 425 | 0.550 |
| 480 | 0.923 |
| 448 | 0.653 |
| 460 | 0.755 |
- Which is the explanatory variable and which is the response variable?
- Make a scatterplot of the response variable against the explanatory variable.
- Based on your scatterplot, as fish length increases, does mercury concentration in fish tissue tend to increase, decrease, or remain about the same? Is this an example of positive or negative association?
- Would you describe the form of the relationship as linear or nonlinear? Explain.
- Why do you think that only fish of edible/legal size were included in the dataset?
11.
(a) Fish length is the explanatory variable; mercury level is the response variable.
A-14
(b)
(c) Increase; positive association
(d) Linear; the dots appear to form a pattern about a
straight line.
(e) The relationship between mercury in fish tissue may be different for fish that are below the edible/ legal size. In terms of health, only the fish that are of edible size pose a health risk if their mercury levels are too high.