Sampling

• What is random sampling? A sophisticated form of sampling in Which all members of the target population have an equal chance of being selected.
• How to carry out random sampling? Obtain a list of all members of the target population. All names on the list are assigned a number. The sample is generated through the use of a lottery method such as a computer based randomiser or picking from a hat.
• Evaluation of random sampling: Free from bias - researcher has no influence over who is chosen(positive). Probibility wise; you are more likely to chose a representative sample (positive). However, it is possible for the method to select 20 female psychology teachers from london called joyce(negative). Difficult and time-consuming as a full list of the target population is difficult to obtain (negative)
• What is systematic sampling? When every nth member of a population is selected, such as every 5th person on the sampling frame.
• How to carry out systematic sampling? A sampling frame is produced (which is a list of people in the target population organised into something like alphabetical order). Then a sampling system (every nth person) is nominated or randomly decided. The researcher then works through the sampling frame until every nth person is chosen.
• Evaluation of systematic sampling? Avoids researcher bias as once the sampling system is chosen, they have no influence over who is selected (positive). Fairly representative (positive). However still possible to get all males (negative). Also is time consuming and difficult to get a sampling frame of the whole target population (negative).
• What is stratified sampling? When the composition of the sample reflects the proportions of people in certain strata (sub-groups) within the target population.
• How to carry out stratified sampling? Identify the different strata that make up the population. The proportions for the sample to be representative are then worked out. The people that make up each stratum are selected using random sampling.
• Evaluation of stratified sampling: Avoids researcher bias because once the strata are made, the people chosen is beyond the researchers control (positive). Produces the most representative sample possible as it accurately reflects the composition of the target population (positive). Extremely time-consuming (negative). Cannot identify all the ways that people are different as it only recognises differences based on one variable/characteristic, so complete representation is not possible (negative).
• What is oppportunity sampling? Simply deciding to select anyone who appears willing and available. The researcher takes the chance to ask whoever is around at the time of the study.
• Evaluation of opportunity sampling: Convenient - less time, money and effort (positive). Unrepresentative of the population as your only taking people from a specific area and cannot be generalised for everyone (negative). Biased as the researcher has full control over who is selected (negative).
• What is volunteer sampling? Where participants select themselves to be part of a sample; hence also known as self-selection. A researcher may place an advert in a newspaper or a common room notice board.
• Evaluation of volunteer sampling: Requires minimum input from the researcher, so less time consuming Asking for volunteers may attract a certain type of peron, such as people that are keen, curious or helpful. Therefore cant be generalised for everyone