1. A oral health education program aimed at promoting oral hygiene was conducted, and 28 adult volunteers with mild periodontal disease were enrolled. The periodontal scores (between 0 and 6) were measured before the program and 6 months after its completion. After 6 months, the periodontal scores of 15 patients had improved (increased scores), those of 8 patients deteriorated (decreased scores), and those of 5 patients remained the same, as given in Table 12.8.
Please answer the following questions:

(a) What is the design of this study?

(b) Is it appropriate to use the paired samples t-test for testing whether the oral health education program could improve the periodontal condition? Why?

(c) Which method could be used for testing the hypothesis? What is the underlying idea of this method. State H0 and H1 .

(d) State the assumptions necessary for the validity of your analyses.

(e) Test the hypothesis using the appropriate method and interpret the results.