The producers of a new toothpaste claim that it prevents more cavities than other brands of toothpaste. A random sample of 60 people used the new toothpaste for 6 months. The mean number of cavities at their next checkup is 1.5. In the general population, the mean number of cavities at a 6-month checkup is 1.73 (σ = 1.12).

a. Is this a one- or two-tailed test?

b. What are H₀ and H_a for this study?

c. Compute z_obt.

d. What is z_cv?

e. Should H₀ be rejected? What should the researcher conclude?

f. Determine the 95% confidence interval for the population mean, based on the sample mean.