Question

You ask a group of 10 adults to participate in a reaction time task concerning verbal comprehension while under the influence of a low dose of amphetamine (one of a variety of “speed” drugs, or central nervous system stimulants). The history of research indicates that performance on many tasks actually improves with low doses, but with higher doses, performance deteriorates). You record the following comprehension times (in seconds) required to identify the two meanings of ambiguous sentences, such as, “The mayor asked the police to stop drinking” or “The children ran in the house.” You hypothesize that the low dose of amphetamine will speed up the participants’ comprehension times (you expect faster/smaller time scores with a low dose of amphetamine, that is). The mean comprehension time on this task for persons who have not ingested any form of stimulant drug is µ = 1.4 seconds. X (comprehension time, in seconds)

1.1

0.8

1.1

0.7

0.9

1.0

1.3

1.2

1.4

0.8

Which of the following are the correct statements of the null and alternate hypotheses, H0 and HA ?

H0: µ = 1.4 and HA: µ 1.4

H0: µ 1.4 and HA: µ = 1.4

H0: µ > 1.4 and HA: µ 1.4

H0: µ 1.4 and HA: µ < 1.4

H0: µ < 1.4 and HA: µ 1.4

H0: µ 1.4 and HA: µ > 1.4

Answer 1

The null hypothesis is

H0: µ = 1.4

Since we need to test that the low dose of amphetamine will speed up the participants’ comprehension times (you expect faster/smaller time scores with a low dose of amphetamine, that is) so

HA: µ < 1.4