The market research firm Salary.com reported that the mean annual earnings of all family practitioners in the United States was $178,258. A random sample of 55 family practitioners in Los Angeles that month had mean earnings of ̄x = $192,340 with a standard deviation of

$42,387. Do the data provide sufficient evidence to conclude that the mean salary for family practitioners in Los Angeles is greater than the national average?

a. State the null and alternate hypotheses.

b. Compute the value of the t statistic. How many degrees of freedom are there?

c. State your conclusion. Use the α = 0.05 level of significance.