A new light bulb is being considered for use in an office wi

A new light bulb is being considered for use in an office with computers. It is decided that the new bulb will only be used if it has a mean lifetime of more than 500 hours. A random sample of 40 bulbs is selected and placed on life test. The mean and standard deviation are found to be 505 hours and 18 hours, respectively. The hypothesis used is: H0: mu=500 vs. Ha: mu>500 What is the test statistic T?

Solution

Formulating the null and alternative hypotheses,              
              
Ho:   u   <=   500  
Ha:    u   >   500  
              
As we can see, this is a    right   tailed test.      
              
              
Getting the test statistic, as              
              
X = sample mean =    505          
uo = hypothesized mean =    500          
n = sample size =    40          
s = standard deviation =    18          
              
Thus, t = (X - uo) * sqrt(n) / s =    1.756820922 [ANSWER]