# A spark plug manufacturer claimed that a new

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3. A spark plug manufacturer claimed that a new manufacturing procedure has changed the mean life of their plugs from 22,100 miles. Assume that the life of the spark plugs follows the normal distribution. A fleet owner purchased a large number of sets. A sample of 18 sets revealed that the mean life was 23,400 miles and the standard deviation was 1,500 miles. Is there enough evidence to substantiate the manufacturer’s claims at the 0.05 significance level?
4. The directors of marketing at Smith Corporation believes that quantity that the company sells is related to Smiths own price and advertising expenditure but is not sure that the relationship is linear. The marketing director collects 26 weekly observations on these variables to estimate the following regression:CoefficientT ValueIntercept5000.000.9801Price-10.01-2.2128Price Squared-0.52-2.9237Advertising40.223.13Advertising Squared-0.81-1.58R2= 0.3357 F = 4.781Fully Evaluate and Interpret these empirical results on the basis of all available statistics (use a 0.05 significance level).