15.

The average gasoline price of Sinclair has been $4.35 per gallon. Recently, the company has undertaken several efficiency measures in order to reduce prices. Management is interested in determining whether their efficiency measures have actually reduced prices. A random sample of 29 of their gas stations is selected and the average price is determined to be $4.20 per gallon, with a sample standard deviation of $0.62. The test will be conducted at the 0.10 significance level.

The critical value is

(round the final answer to two decimal places, e.g. 2.57)