This is a sample lab report. It was also an attempt to see if a normal doseof caffeine would have a noticeable effect on reaction time. (I have includedsome comments about the report in red. I spent about 2 1/2 hours writingthis up.) An on-line reaction test was performed before drinking a cup of coffee, afterabout half of the coffee was consumed, and then again after the coffee wasfinished in order to try and observe the effects of caffeine on reaction time.
(The test used was the one for Firefox users on the lab web page .) Theresults were analyzed statistically. The coffee used was Tim Horton’s, fromthe kiosk in the Science building at WLU. The experiment was performed atabout 2:00 on a Friday afternoon. The experimental subject, (the author),had not consumed any coffee for a few hours prior to the experiment.
The amount of coffee was about 320ml. (The experiment was a sudden idea, and so some experimental details are not as specific as they might be ina more carefully planned experiment.) An uncertainty of 30ml in the volumeis probably reasonable, mostly due to having to estimate after the fact sincethe coffee cup was not graduated.
About 7±1 minutes passed during the drinking of the first half cup, and about 12±1 minutes passed during the drinking of the second half cup. Theuncertainty in the time was relatively large since the amount of time takento drink the coffee was not considered an important variable and so was notmeasured precisely.
Since no uncertainty is given for the reaction time tester, but all times aregiven to 0.001s, an uncertainty of 0.001s has been assumed for these calcu-lations.
Note that in Table 1 the two average times agree within their uncertain- ties. (If I were going to include sample calculations of ¯ do it here. I used a spreadsheet, so the calculations only took me about 10minutes. ) After drinking a half cup of coffee, and repeating the test, as shown in Table 2, the average times are shorter. Note that the two repetitions of thetest agreed with each other within their uncertainties, as in the case beforecoffee above, however, they did not agree with the average times before coffee.
The reaction time was shorter after one half cup of coffee.
The test was repeated after all of the coffee was consumed, and again the two tests agreed with each other within uncertainties. The results are shownin Table 3. Again, however, the results did not agree with the results in theprevious case. In other words, after all of the coffee the reaction times did notagree with the times after half of the coffee. The reaction times were longerafter a cup of coffee than after one half cup of coffee. (This was somethingI had not expected. I thought that if any effect was observable, it would bemonotonic; ie. more coffee would have a greater effect.) Since each pair of 5 trials were consistent, they can be combined into 3 sets of 10 measurements, as shown in Table 4. Note that the results for setsof 10 are consistent with the results for sets of 5; the average after half a cupdoesn’t agree with the times before or after, although the before and aftertimes agree with each other.
As has been previously stated, this experiment was not planned in advance,so there is a greater uncertainty in both the time taken and the volume ofcoffee consumed than would have been the case otherwise. However, since theintention was to see if an effect was noticeable, this is acceptable. The uncer-tainty in the reaction time measurements was actually quite small, enoughthat a few things can be noted. First of all, in each of the 3 cases, (before,halfway through, and after coffee), the two sets of 5 trials agreed with eachother within uncertainties, so the amount of coffee consumed seems more im-portant than other factors such as how many times the test had previouslybeen performed. Second, the change in the average times from before thecoffee to after half a cup is significant, and so it suggests that the coffee itselfwas the important difference. The most unexpected result was that the aver-age times after coffee agreed with the times before coffee, but not with thoseafter 1/2 cup. This may indicate that there is more than one process at work.
To improve this experiment, along with taking more careful measurementsof the volume of coffee, it would be useful to ensure that the subject hashad no coffee for at least 12 hours prior to the experiment. It would also beuseful to substitute a non-caffeinated hot drink, such as herbal tea, to see ifthe effect may be due to hot water rather than coffee specifically. Performing the experiment at different times of day, as well as on both an empty and afull stomach would help to potentially eliminate other variables.
Before coffee, reaction time was measured to be ¯ After one half cup of coffee, reaction time was measured to be ¯ After one cup of coffee, reaction time was measured to be ¯ The times before and after coffee agree within their uncertainties. The timesbefore and after 1/2 cup don’t agree. There is a difference.
The times after 1/2 cup and after a whole cup also don’t agree. There is a difference.
Because of these differences, it would appear caffeine does have a signifi-cant effect on reaction time, although it appears to be more complex thananticipated.


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