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On a separate sheet of paper, solve each of the following problems (show your work).
The company General Electric claims that, on average, a certain brand of its flashlight battery provides
at least 300 hours of use. A researcher suspects that the population of batteries has a mean that is less
than 300 hours. She selects a random sample of 49 batteries and obtains a sample mean of 290 hours
and a sample standard deviation of 70 hours. Use the data to test the researcher’s claim at a 5%
significance level that the mean is less than 300 hours.
Data published by California on the salaries of state workers indicate the average yearly salary of fulltime secretarial staff at state universities is $47,500. A sample of 64 full-time secretaries working for
CSULA generates a mean of $49,000 and a standard deviation of $6,200. Use the data and a 5%
significance level to test whether the mean salary for secretarial staff at CSULA is different from the
state mean.
The Lays potato chip factory has added a new machine which fills snack-pack sized bags of potato chips.
The machine is supposed to put an average of 28.3 grams of chips in the bags it fills, but a quality control
manager working at Lays believes the machine is overfilling the bags. A random sample of 36 bags filled
by the machine had a mean of 29.1 grams and a standard deviation of 0.9 grams. Use a 1% significance
level to test the claim that the machine is overfilling the “28.3 gram” bags of chips.