Psy: Sampling and Hypothesis

Psy: Sampling and Hypothesis

1. Sampling methods

   • Opportunity sampling: easiest, cheapest and most common method of sampling which makes use of people that are readily available and are willing to take part
     • Strength: It is the easiest and quickest way to obtain participants as psychologists will use participants that they have access to
     • Weakness: It is likely to produce a bias sample as the participants are usually from the psychologists own social/cultural group so only certain types of people will be selected. It is not very representative
   • Volunteer/self-selecting sample: people who want to take part in the research volunteer themselves in response to an advert that the psychologist has distributed. People who were interested would reply and the psychologist would them filter the responses in order to gain the most representative sample
     • Strength: It allows the researcher to access a wider target population and a wider range of potential participants
     • Weakness: it is a bias method as people tend not to respond to adverts unless they have a strong interest/view to share or motivation to take part and are therefore more likely to respond with demand characteristics
   • Random sampling: it is the hardest of all three, especially with a large target population as the researcher needs the names of all the target population to do this. All potential participants are entered into a draw of some kind and names are randomly selected until the desired number of participants are chosen. Participants are then contacted to take part
     • Strength: this is the least bias method as all members of the target population have an equal chance of being selected
     • Weakness: it is difficult and time consuming to do especially with large target populations, for example you could not do this if the target population was all males aged 21-31

2. The aim of the study refers to the intentions of the study whereas the hypothesis is a testable statement that essentially predicts what the researchers expect the study will find. Hypothesis only apply to experiments and correlations

3. Experiment vs correlation

   • Experimental hypothesis: would predict some sort of difference will occur between the variables and so predicts the effects of the IV and DV
   • Correlational hypothesis: would predict that there would be a relationship between 2 variables. You use a correlational hypothesis for a correlation study

4. Different types of hypothesis

   • One tailed (directional)
     • Predicts a specific direction of results
     • For example: 'Female participants will correctly identify significantly more emotions in the photographs of the faces than male participants'
   • Two tailed (non-directional)
     • Predicts that a difference/relationship will be found but are non-directional in terms of what will be specifically found so does not say what the difference will be
     • For example: 'there will be a significant difference between males and females in the number of emotions correctly identified in the photographs of the faces'
   • Null
     • States that no difference/relationship will be found
     • For example: 'there will be no significant difference between males and females in the number of emotions correctly identified on the photographs of faces and any difference will be due to chance