5.15 The authors of the paper “Statistical Methods for Assessing Agreement Between Two Methods of Clinical Measurement” (International Journal of Nursing Studies

[2010]: 931–936) compared two different instruments for measuring a person’s ability to breathe out air.

(This measurement is helpful in diagnosing various lung disorders.) The two instruments considered were a Wright peak flow meter and a mini-Wright peak flow meter. Seventeen people participated in the study, and for each person air flow was measured once using the Wright meter and once using the mini-Wright meter.
Subject Mini-
Wright Meter Wright Meter Subject Mini-
Wright Meter Wright Meter 1 512 494 10 445 433 2 430 395 11 432 417 3 520 516 12 626 656 4 428 434 13 260 267 5 500 476 14 477 478 6 600 557 15 259 178 7 364 413 16 350 423 8 380 442 17 451 427 9 658 650

a. Suppose that the Wright meter is considered to provide a better measure of air flow, but the mini-Wright meter is easier to transport and to use. If the two types of meters produce different readings but there is a strong relationship between the readings, it would be possible to use a reading from the mini-Wright meter to predict the reading that the larger Wright meter would have given.
Use the given data to find an equation to predict Wright meter reading using a reading from the mini-Wright meter. (Hint: See Example 5.4.)

b. What would you predict for the Wright meter reading of a person whose mini-Wright meter reading was 500?

c. What would you predict for the Wright meter reading of a person whose mini-Wright meter reading was 300? (Hint: See discussion of extrapolation that follows Example 5.4.)