Assume you are an Intern at Consumer Reports Magazine assigned to evaluate the c
ID: 3219001 • Letter: A
Question
Assume you are an Intern at Consumer Reports Magazine assigned to evaluate the claim from Apple that the average battery life length for the new IPhone is at least 8 hours on 4G with standard usage. You find all the IPhone distribution centers and select five IPhones from each totaling 25 IPhones for your sample. You test the batteries of your total of 25 phones and get the following results for battery length before charging was required (in hours):
4.5, 6, 8, 5.5, 7, 5, 7.7, 6, 8.5, 7.5, 5, 9, 8, 6.5, 5, 7, 8, 6.5, 5.5, 6, 6.5, 8.5, 5, 5.5 ,7.5
Explanation / Answer
Standard deviation of the sample(s)=1.313.
Sample mean=6.608
SE = s / sqrt( n )
=1.313/sqrt(25)=0.2626.
DF=24
t = (xmean - ) / SE
=(6.608-8)/0.2626
=-5.3.
calculating p value from t statistic we get 0.00001948<0.005 hence we can reject the claim.