sampling

• population is the group of individuals the researcher is interested in
• sample is a smaller group taken from the population that researcher is interested in
• it is important that the sample taken for research so representative of the target population so that generalisations of the findings to target population can be made
• the different sampling methods include:

  • opportunity sample
  • random sample
  • stratified sample
  • systematic sample
  • volunteer sample
• opportunity samples are where you recruit people who are most convenient or most available
• opportunity sample strength

  • easiest method because you find first suitable participants you can find
  • takes less time than other methods
• opportunity sample limitation

  • biased as it is draw from small part of population
  • can vary depending on where to go or time of day
• random sampling is a method that includes the lottery method - a random number table or random number generator used to pick out sample
• random sampling strength

  • unbiased because all members of target population have equal chance of selection
• random sampling limitation

  • time consuming - need to have list of all members of population and conduct those selected which will take time
• stratified sampling is where subgroups (strata) within population are identified (age groups)

  • participants are obtained from each strata in proportion to occurrence in population - done using random technique
• stratified sampling strength

  • likely to be more representative than other methods because1 there is proportional and randomly selected representation of subgroups
• stratified sampling limitation

  • time consuming to identify subgroups then randomly select and contact participants
• systematic sampling is where researchers use predetermined system to select participants such as selecting every '3rd' person from a list
• systematic sampling strength

  • unbiased as participants are selected using an objective system
• systematic sampling limitation

  • not truly unbiased/ random unless select number using random method and start with this person when selecting
• volunteer sampling is where you advertise in newspaper, online and ask those interested in participating to contact you
• volunteer sampling strength

  • gives access to variety of participants which may make sample more representative and less biased
• volunteer sampling limitation

  • sample still biased as participants might have more time or more motivated or need money (volunteer bias)
• using random techniques ensures researcher is collecting completely unbiased data and there are no patterns existing
• random techniques include

  • lottery method
  • random number table
  • random number generations
• sampling bias is were all sampling methods are biased or distorted in someway
• volunteer bias is the fact that people who volunteer take part in research are likely to be different to other members of population and this distorts/biases the data being produced