non random sampling techniques

quota sampling

• quota sampling : is like stratified sampling , but with an important variation

• in this case, the researcher decides how many of each category of person should be included in the sample , but then, instead of selecting them at random from a sampling frame , the researcher goes out looking for the right number of people in each category until the quota is filled

• thus , if in a sample of 500 people, the quota of women aged between 30 and 40 is 22 , the researcher will look for 22 women and when they have been interviewed , that is the quota filled

• method used by market researchers, and by television news companies and newspapers to find out what peoples voting preferences are before an election

disadvantage of quota sampling

• because it lacks some randomness, there is a danger that bias might creep into the selection of the sample; researchers may only stop and question people who look ‘suitable’ or ‘cooperative’ or visit homes that loom ‘respectable’

• consequently , it is doubtful whether this sampling technique is able to gather a sample that is truly representative of the research population

purposive sampling

• involves researchers choosign individuals or cases that fit the nature of the research

• purposive sampling occurs when a researcher chooses a partiular group or place to study because it is known to be of the type that is wanted

• goldthorpe and his team wanted to stufy manual workers with high incomes to see whether they had developed a middle class way of life

• the purposely decided to study workers employed by a car manufacturer in luton because these manufacturers

opportunity sampling

• similar to purposive sampling

• it essentially means making the most out of situations or opportunities in which the research population is likely to be found

• for example, if the researcher is interested in researching if african people experience racism in the uk , there is little point in the researchers standing around city centres hoping that african people might come along and fulfil their quota

• it is also very unlikely that a sampling frame of african people is available to researchers

• a better alternative would be to identify opportunities in which there is more chance of coming into contact with african people

• researchers might therefore head down to churches or community centres that cater for african people and purposely ask all of those present to take part in the research

snowball sampling

• mainly used when researchers experience difficulty in gaining access to a particular group of people whom they wish to study because there is no sampling frame available or because the research population engage in deviant or illegal activities that are normally carried out in isolation or in secret

• this sampling technique involves finding and interviewing a person who fits the research needs and then asking them to suggest someone else who might be willing to be interviewed

• in this way, the original small nucleus of people grows by adding people to it in stages , much as a snowball can be built up b rolling it along the snow on the ground

• the sample can grow as large as the researcher wants

volunteer sampling

• a variation on snow ball sapling

• sociologists may advertise for research volunteers in magazines and newspapers on university noticeboards or on the internet

• however, both snowball and volunteer sampling may fail to produce representative samples

• the people who take part in the research may not be typical of the research population that the sociologist is interested in