Two competing headache remedies claim to give fast-acting relief. An experiment was performed to compare the mean lengths of time required for bodily absorption of brand A and brand B. Assume the absorption time is normally distributed. Twelve people were randomly selected and given an oral dosage of brand A. Another 12 were randomly selected and given an equal dosage of brand B. The length of time in minutes for the drugs to reach a specified level in the blood was recorded. The results follow: x s x n Brand A 20.1 8.7 12 Brand B 18.9 7.5 12 a) Is there sufficient evidence that these drugs differ in the speed at which they enter the blood stream?