Psychology, Stress and the Immune system

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Abigail Pratt and Nicky Griffiths


The researcher aimed to find out whether caffeine levels have any affect on reaction time. The researcher’s experimental hypothesis is that higher caffeine levels will cause slower reaction times. The researcher’s null hypothesis is that caffeine levels will have no effect on reaction times.


The researcher used an experimental method called a lab experiment and the experiment design that was used was an independent group design. The researcher used 15 participants from Ossett Sixth Form College that were attending their regular AS level Psychology class. The participants were aged between 16 and 17. The researcher used a technique known as an opportunity sample. Opportunity sampling is the sampling technique most used by psychology students.  It consists of taking the sample from people who are available at the time the study is carried out and fit the criteria you are looking for. 

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  • The researcher asked the participants to split into pairs. They were then asked to split themselves randomly into group A and group B.
  • The sample was then divided. Group A were given a caffeine based drink and Group B was given a caffeine free drink. The participants from both groups were asked to drink their drinks at the same time.
  • The participants were left for 15 minutes. This was so that the caffeine, if it did have an effect on reaction time, had time to get into their bodies and take affect.
  • Each participant then did something ...

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