For years the Brite Lite Company has made light bulbs that h

For years, the Brite Lite Company has made light bulbs that have had an average lifespan of 800 hours of use. Recently, some changes were made in the design and the production of the light bulbs. It is thought that the lifespan of the light bulbs has been increased by the changes. A random sample of 55 new light bulbs is selected and tested. The sample average bulb life is 910 hours with sample standard deviation 126 hours. Does this indicate that the population mean bulb life has increased? The correct hypothses for this test are

H_O: mu = 800

H_A: mu = 910

H_O: mu = 800

H_A: mu > 800

H_O: mu = 800

H_A: mu < 800

H_O: mu = 910

H_A: mu = 800

Solution

HO: mu = 800

HA: mu < 800