The average monthly cell phone bill was reported to be $50.07 by the U.S. Wireless Industry. A random sampling of a large cell phone company found the following monthly cell phone charges (in dollars):
55.83 49.88 62.98 70.42
60.47 52.45 49.20 50.02
58.60 51.29
At the 0.05 level of significance, can it be concluded that the average phone bill has increased?
(Note: The value of the sample mean (x ≈ $56.11) and sample standard deviation (s ≈ $6.97) are calculated.)
a) State the hypotheses.
b) Find the critical value and state the number of degrees of freedom.
c) Compute the test value. What is the Pvalue interval?
d) Make the decision.
e) Summarize the results.