4. A factory manufactures treadmills and has a warranty of 5 years on their products. An engineer at the factory believes that the treadmills do not last that long and will malfunction in less than 5 years.
He tests a sample of 40 treadmills and find the average time to be 4.8 years with a standard deviation
of 0.50. (5 points)
a. State the null and alternative hypotheses
b. At the 95% confidence level, is there enough evidence to support the engineer's claim?

(01.03 mc) which of the following is a step in simplifying the expression x multiplied by y to the power of 2 over x to the power of negative 3 multiplied by y to the power of 3, the whole to the power of negative 4. select one: a. x to the power of negative 4 multiplied by y to the power of negative 2, the whole over x to the power of negative 7 multiplied by y to the power of negative 1. b. x to the power of negative 4 multiplied by y to the power of negative 8, the whole over x to the power of 12 multiplied by y to the power of negative 12. c. x to the power of negative 4 multiplied by y to the power of negative 8, the whole over x to the power of negative 3 multiplied by y to the power of 3. d. x to the power of negative 4 multiplied by y to the power of negative 2, the whole over x to the power of negative 3 multiplied by y to the power of 3.