Exercise 2.17 on page 55 describes a study in which scientists train dogs to smell cancer. Researchers collected breath and stool samples from patients with cancer as well as from healthy people. A trained dog was given five samples, randomly displayed, in each test, one from a patient with cancer and four from healthy volunteers. The results are displayed in Table 3.14. Use StatKey or other technology to use a bootstrap distribution to find and interpret a 90% confidence interval for the difference in the proportion of time the dog correctly picks out the cancer sample, between the two types of samples. Is it plausible that there is no difference in the effectiveness in the two types of methods (breath or stool)?

Table 3.14

Exercise 2.17

Scientists are working to train dogs to smell cancer, including early stage cancer that might not be detected with other means. In previous studies, dogs have been able to distinguish the smell of bladder cancer, lung cancer, and breast cancer. Now, it appears that a dog in Japan has been trained to smell bowel cancer. Researchers collected breath and stool samples from patients with bowel cancer as well as from healthy people. The dog was given five samples in each test, one from a patient with cancer and four from healthy volunteers. The dog correctly selected the cancer sample in 33 out of 36 breath tests and in 37 out of 38 stool tests.

Breath Test Stool Test Total Dog selects cancer Dog does not select 70 33 37 3 4 cancer Total 74 36 38 4.