Does Coffee Have an Effect on Reflexes?

This experiment was done to find out if coffee has an effect on reflex times.

Subjects were randomly selected to test their reflex time before and after having a cup

of coffee.

Taryn Alkis

AP Statistics

May 28, 2013

2012 – 2013 School Year

Coffee has been known to make you more alert and can also help increase your

reaction time. It is a popular stimulant which is used throughout the world. This

experiment would be interesting for a person who would like to see if their reflexes or

performance improved after drinking a cup of coffee. In the article “Does Caffeine Effect

Your Reflexes?” it is explained how numerous studies conclude that caffeine can

improve reaction times within minutes or even seconds (Thorne). Therefore, this test

will prove if coffee increases your reaction time after drinking a cup of coffee.

This experiment was conducted with 30 households in Travis Country which

were randomly selected by giving each house a number from 1 to 1409 shown in

Appendix A. A random number generator was then used to randomly select 30 houses

to test. Subject’s reflexes were recorded, shown in Appendix B, by repeating the ruler

test on each subject three times before and after drinking a cup of coffee and then

taking the average. As the subject was standing, a twelve inch ruler was dropped one

inch above the subject’s dominant hand. The subject would then catch the ruler quickly

as possible with only their thumb and index finger. Where the ruler was caught, in

inches from the bottom of the ruler, was recorded as their reflex. The subjects would

then drink a cup of coffee, wait a minute, and then their reflexes were tested with the

ruler once again.

Because the claim that caffeine increases each individual person’s reflexes, a

dependent two-sample means hypothesis test with a significance level of 5% will be

used for this experiment. A significance level of 5% was chosen because there is

nothing medical about this experiment so a neutral level was chosen. After the

hypothesis test was conducted as shown in Appendix C, with a p-value so low it was

revealed that coffee increases an individual’s reflexes. Although this neighborhood may

be a large population, it may not be representative of the whole community because

they may already have fast reflexes due to something going on in their daily lives that

involve fast reflexes like sports.

It has been learned through this experiment that coffee helps increase reflexes.

Overall, coffee can stimulate your body making the subjects react quicker resulting in

increased reflexes. Conducting this experiment has shown that coffee can help

increase reflexes but there also may be confounding variables relating to faster reflexes

as well. If this experiment was run again, to have less confounding variables, a two-

sample independent hypothesis should be conducted where there are two groups. One

group’s reflexes would be tested without coffee or any caffeine, and the other group’s

reflexes would be tested with coffee.

Since the subjects tested may have already had coffee in their system, the first

time their reflexes were tested may have appeared to be better than they would be

without having any coffee or caffeine in their system at all. Another variable that might

have caused better reflex times was muscle memory, or people even anticipating for

when the ruler was going to drop. Coffee is known to make people more alert though,

so it is true that coffee is a definite reason for increased reflexes. There are multiple

variables that could have caused the subject to have increased reflexes but coffee is

definitely one.

WorksCitedRuler Drop Test. 1 May 2013. <http://www.brianmac.co.uk/rulerdrop.htm>. 

Thorne, Roger. "Does Caffeine Effect Your Reflexes?" 8 Augus 2011. 

<http://www.livestrong.com/article/510954‐does‐caffeine‐affect‐your‐reflexes/>. 

 

Appendix A

Travis Country Neighborhood Map

Appendix B

Data and Signatures

Appendix C

Calculations