For the following exercises where applicable:

a. State the hypotheses and identify the claim.
b. Find the critical value(s).
c. Compute the test value.
d. Make the decision.
e. Summarize the results.
Use the traditional method of hypothesis testing unless otherwise specified. Assume all variables are normally distributed.

The standard deviation of the pollution by-products released in the burning of 1 gallon of gas is 2.3 ounces. A random sample of 20 automobiles tested produced a standard deviation of 1.9 ounces. Is the standard deviation really less than previously thought? Use α = 0.05.