3.13 A recent study (by R. Armenio et al., J. Am. Dent. Assoc. 139: 592-597, 2008) re-

ported results of a double-blind randomized clinical trial comparing tooth sensitivity for 14 patients using a fluoride gel to 15 patients using placebo. Each patient had weekly visits for responses, between 3 and 7 times. The authors reported a 2 x 2 table having counts (11, 57) for placebo and (21, 62) for fluoride gel for the (yes, no)

response on tooth sensitivity. They reported a P-value of 0.2 for a chi-squared test comparing the two treatments. Discuss the suitability of this analysis. [Hint: Are the observations independent?]

Table 3.12 Results for Exercise 3.12 on Party ID and Gender Expected Frequency female dem indep repub 422 381 273 393.41 407.05 275.55 male 299 365 232 327.59 338.95 229.45 Statistic Chi-Square Value DF 2 8.2943 0.0158 Prob Likelihood Ratio Chi-Square 2 8.3090 0.0157 Observ Resraw Reschi StReschi Observ Resraw Reschi StReschi 1 28.59 1.58 2.69 4 28.59 1.44 2.69 2 26.05 1.41 2.43 5 -26.05 -1.29 -2.43 3 2.55 0.17 0.26 6 -2.55 -0.15 -0.26 Table 3.13 Data for Exercise 3.14 on Psychiatric Diagnoses Diagnosis Schizophrenia Affective disorder Neurosis Personality disorder Special symptoms Drugs No Drugs 105 8 12 2 18 19 47 52 0 13 Source: Reprinted with permission from E. Helmes and G. C. Fekken, J. Clin. Psychol. 42: 569-576, 1986.