Caffeine Junkies: Effects of caffeine on wordsearch task performance of Dartmouth Students

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Caffeine Junkies Effects of caffeine on
word-search task performance of Dartmouth
Students

• Coffee creative lighter fluid. --Floyd
  Maxwell (1957-)

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Research Rationale

• We find that many of our friends consume
  caffeinated beverages prior to engaging in
  academic tasks, exams, or other performance
  evaluations with the belief that the stimulant
  will improve performance and enable them to focus
  to a higher degree on the task at hand. We have
  designed an experiment in which we examined the
  actual effects of caffeine on the performance of
  a simple verbal/spatial task (a word search
  test). The experimental topic may have
  implications on the effects of caffeine in a
  college academic testing environment.

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Our Hypotheses

• Null Hypothesis
• Consumption of a tall (355mL) caffeinated coffee
  will have no effect of the number of words, or
  have a negative effect on the number of words,
  found in a simple word search test in a two
  minute time period.
• Alternate Hypothesis
• Consumption of a tall (355mL) caffeinated coffee
  will improve performance, i.e. increase the
  number of words found in a simple word search
  test in a two minute time period.
• "Coffee falls into the stomach ... ideas begin to
  move, things remembered arrive at full gallop ...
  the shafts of wit start up like sharp-shooters,
  similies arise, the paper is covered with ink
  ..." -- Honore de Balzac

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Parameter

• If you choose a subject at random from the
  Dartmouth College undergraduate student body,
  then there is some degree to which caffeine will
  improve his/her performance on a verbal/spatial
  task. This mean score is the average number of
  words found by participants after drinking
  caffeinated coffee ?-caff. The parameter that
  we tested is the difference between ?-caff and
  the average number of words found by participants
  after drinking non-caffeinated coffee, ?-non.
  Under the null hypothesis, caffeine will not
  increase the number of words found in the simple
  word search task hence the null hypothesis is
  that ?-caff ?-non, while the alternate
  hypothesis is that ?-caff ?-non.
• Please note that the subjects were NOT in fact
  chosen at random for our initial testing
  Participants were selected on the basis of their
  presence at Collis student center on the evening
  of our testing, and whether or not they agreed to
  be a part of our study (i.e. whether they had
  sufficient time to take our test, and had the
  desire to drink coffee specifically).

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Experimental Equipment 1

• Our materials were as follows
• 1 testing site. This was a large, common room,
  with a certain degree of noise and student
  traffic. This was NOT a controlled environment.
• 17 identical coffee cups
• 3 pens available for students taking the word
  search test
• 1 blue highlighter
• 9 cups of caffeinated coffee brewed by Collis
  Café (all from one batch of coffee)
• 8 cups of decaffeinated coffee brewed by Collis
  Café (all from one batch of coffee)
• 17 copies of a simple word-search task. NOTE
  All subjects completed identical word searches.
  The word search used for experimentation was
  chosen due to its unusual subject matter,
  astronomy we hope to avoid any advantage in word
  recognition, i.e. the words to be found should be
  equally familiar to most college students (not
  derived from any specific movie, hobby, or area
  of expertise that some students are more likely
  to be familiar with than others).
• 1 watch, to time the wait period as well as the
  word search testing period
• Coffee should be black as hell, strong as death,
  and as sweet as love. --Turkish proverb

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The task...
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(No Transcript)
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Experimental Equipment 2

• Our experiment required the following personnel
• 1 Pourer. Pourer duties include pour coffee
  (caff and non) into cups, label the bottom of the
  decaffeinated cups with a blue pen.
• 2 Distributors. Distributor duties include give
  subjects the coffee cups. The distributors are
  blind to the coffee condition, with no knowledge
  of which color marking corresponds with which
  cup. The distributor also hands out the word
  search task, and keeps time the initial
  15-minute wait period, as well as the 2-minute
  testing period.

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Experimental Procedure
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Experimental Procedure 1

• Our Experimental Protocol was as follows One
  experimenter approached potential participants in
  Collis student center, and asked them if they
  would be willing to be a part of a brief,
  17-minute experiment in which they would drink a
  full cup of coffee and engage in a short word
  search task. Once students were recruited for
  participation, the pourer filled and marked as
  caff or non 17 cups (total). The distributors
  then handed out the cups of coffee to willing
  subjects, and timed a waiting period of 15
  minutes. Participants were instructed to drink
  the coffee but to keep their cups.
• Decaf Used to sober up after a night on
  non-alcoholic beer! - Unknown

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Experimental Procedure 2

• 17 subjects total participated in the experiment
  (9 caffeinated experimental subjects, 8
  non-caffeinated control subjects).
• Research has shown that caffeine reaches its
  densest concentration in the blood 15 to 45
  minutes after consumption this is the reason we
  imposed a 15-minute wait period after
  participants finish the coffee. Participants
  remained in the same seat during this period
  (although they were permitted to talk to others,
  read, do homework, etc.)

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Experimental Procedure 3

• After the 15-minute wait period delay, the
  distributor handed out the word search task, as
  well as pens, to the participants. Subjects were
  instructed to find and circle as many words as
  possible during a two minute time period.
• At the end of this 2-minute period (measured by
  the Distributors with watches), subjects were
  instructed to put their pens down and the
  Distributors collected the word search tests and
  the cups.
• The distributors and pourer then recorded the
  number of words found on each puzzle. Subjects
  identity was anonymous, with all data coded
  according to experimental status (caff or non).
• "It is inhumane, in my opinion, to force people
  who have a genuine medical need for coffee to
  wait in line behind people who apparently view it
  as some kind of recreational activity." -- Dave
  Barry

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Caffeine is it helping students or just an
addiction?

• It is caffeine alone that sets my mind in
  motion. It is through beans of java that thoughts
  acquire speed, that hands acquire shakes, that
  shakes become a warning...I am...IN CONTROL...OF
  MY ADDICTION! -- From the Minicon Graffiti Wall,
  1989

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Statistical Analysis Preliminary test statistic

• Our primary analysis goal was to determine
  whether or not the difference between the average
  number of words found for each independently
  sampled group is significant.
• Due to the fact that our sample size was
  extremely small (n-caff 9, n-non 8) we
  implement a t-test for the significance of the
  difference between means.
• We assume that the two populations (people who
  ingest caffeinated vs. non-caffeinated beverages)
  are normally distributed, and that they have
  equal standard deviations. (s-caff s-non)

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Descriptive Statistics

• After collecting data, we found the following
  average scores for our experimental (caffeinated)
  and control (non) groups
• X-caff 6.33
• X-non 5.38
• We also calculated variance with the following
  equation
• s2 (x x)²
• (n 1)
• This gave us the following resulting variances
  for each group
• s2 -caff 6.945
• s2 -non 2.839

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Statistical Analysis Significance level

• Since we wanted to be able to report these
  results as statistically significant, we chose
  the significance level to be 0.05. In other
  words, we left only a 5 chance of a type 1
  error. In this setting, a type 1 error
  corresponds to concluding that caffeine improves
  Dartmouth students performance on a word search
  test, when in fact there is no improvement. The
  equation we used to determine whether or not the
  difference in average number of words found from
  the two groups is significant is
• t x-caff x-non _
• v(s2²/n-caff) (s2/n-non)
• when s2 (n-caff 1)s-caff2 (n-non
  1)s-non2
• n-caff n-non 2

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t-score

• For s2 (9 1)(6.945) (8 1)(2.839)
• 9 8 2
• s2 5.029
• Therefore
• t 6.33 5.38
• v(5.029/9) (5.029/8)
• t 0.877

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Degrees of Freedom

• Using the t-table, we must take into account the
  degrees of freedom. Due to the fact that we have
  two samples, we find that
• df n-caff n-non 2
• df 9 8 2
• df 15

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Statistical Analysis Critical region

• Because our Alternate Hypothesis is that ?-caff
  will be significantly greater than µ-non, we are
  only concerned with the critical region under the
  right-sided tail of our distribution, at the .05
  significance level. Therefore, to find the
  critical region, we use degrees of freedom (dF
  15) and the t-table (see Appendix A of our class
  text) to find the area under the standard normal
  curve equal to the significance level of 0.05.
• The critical region for our experiment, given the
  following
• Null hypothesis ?-caff ?-non
• Alternate hypothesis ? -caff ? -non
• Significance level ? 0.05
• Thus the Critical region is t 1.753

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INsignificant results!

• Because our calculated t value of 0.877 does not
  fall within the above critical region, the
  difference between the means of our two groups
  (caffeinated and non-caffeinated) is NOT
  significant at the 0.05 level.
• As we discussed in our proposal, we expected not
  only that caffeinated subjects would find a
  significantly higher average number of words in
  their word search test, but also that the power
  of our hypothesis would be approximately 40
  (i.e. caffeinated subjects would find at least
  40 more words than would subjects given a
  non-caffeinated beverage). Given our results,
  the likelihood that caffeine does in fact help
  subjects on a word search task, to the extent
  that we believed it would, is extremely low.

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Confounding factors 1

• Our experiment dealt with the question of how
  caffeine affects performance amongst Dartmouth
  College students. Unfortunately, we were unable
  to conduct an experiment in which all variables
  were controlled, or which was extensive enough,
  to truly draw any conclusions on this topic.
• Our primary difficulty is rooted in our extremely
  small sample size. The optimum size for a
  two-independent-sample test is N-1 N-2 60.
  We had hoped to include at least 30 participants
  in each group (caffeinated and non-caffeinated
  subjects) however, we were unable to recruit an
  adequate number of participants.

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Confounding factors 2

• A second confounding factor in the implementation
  of our experiment was our inability to control
  the participants caffeine consumption prior to
  testing. We would have liked to recruit subjects
  at least 24 hours before testing, and to have
  instructed them to refrain from ingesting
  caffeinated substances. However, due to time
  constraints, our experiment was conducted without
  knowledge of our subjects blood caffeine
  content. This may have affected our results.
• Additionally, we did not recruit a random sample
  for our testing. Participants were selected on
  the basis of their presence at Collis student
  center on the evening of our testing, and whether
  or not they agreed to be a part of our study
  (i.e. whether they had sufficient time to take
  our test, and had the desire to drink coffee
  specifically).

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Confounding factors 3

• Finally, although our test was double-blind (one
  student poured the coffee, and differentiated
  between caffeinated and non-caffeinated, while
  the other two students distributed the coffee) in
  order to avoid all experimenter bias we would
  have liked to have a non-affiliated math 5
  student to keep time, pass out the tests, and
  collect the tests and coffee cups. We also would
  have preferred making our own coffee, so that we
  could have measured caffeine concentration.
  Also, we did not measure the volume of coffee
  given to each participants, although we made a
  visual approximation to the best of our skill.

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Conclusion

• In conclusion, although we were disappointed that
  our experiment did not yield significant results,
  we believe that the topic of caffeine consumption
  and effects on student health and academic
  welfare should be further explored in more
  controlled studies. Some possible areas of
  research include what are student perceptions of
  the effects of caffeine consumption, and are
  these perceptions correct? What are the effects
  of continued caffeine use across the college
  years? And finally, why does Dirt Cowboy close at
  like 4pm when I need my coffee at 11pm? -)