Question

convenience samples, snowball samples, and quota samples. Provide a definition and explanation of these three sampling methods. Provide a detailed example of the sampling methods that you have defined.

Answer 1

convenience sampling method:- it is a non probability sampling method in which sample is taken from the group which is seem to be easy to approach or reach or contact. in this people are included who are easy to reach. it is also known as grab sampling or accidental sampling. it this you can survey people from school, colleges, work place, local mall, grocery store etc. it does not include random selection of people.

advantages:- it is quite simple and ease of research of sample, cheapest sampling method, helpful for hypothesis generation, data collection can be done in short period of time.

disadvantages:- have little credibility, data biasing is there, high level of sampling error, possibilty of over or under presentation of the population.

for example:- a person want to conduct a survey to know about the employees' thinking of Walmart about their wages. in this case he will not be able to get the list of the employees so to conduct his survey he has to resort to standing outside of the company and has to wait for the coming out of the employees from Walmart company so that he can ask from them. he has to grab whichever employees are coming out. i.e. grab sampling. or if a person wants to know about the satisfaction level of people regarding the services of a grocery store then he has to wait on the outside of the store and has to collect data from the customers who are coming out from that store because he has no knowledge about store' customers.

Snowball sampling method:- it ia also a non probability sampling method in which participants are recruited directly by research participants for the test or study. it is used in the situation when the potential participants are very difficult to find. in this group of people recommend the participants or participants are to be recruited. then recruited participants recommends further participants then again selected participants recommends additional participants and the process is going on and builiding up like a snowball which is rolling down a hill. in this participants should not ask to identify additional participants infact they should be asked to encourage other people to come forward. this is also called referral sampling method or chain sampling method. the success of this method is totally dependent of first sample as he gives further references.

advantages:- requires minimum human resources, no need of additional planning, affordable, simple process, possible to sample population which are not easy to access

disadvantages:- no way to know the preciseness because of the lack of guaranteed representation, unchecked sample size, lack of control over the selection of sample as sample is reffered by participants, risk of community bias, impossible to determine sample error.

for example:- to survey on group of people who are suffering from AIDS. the people who are suffering from AIDS are limited and do not want to disclose their disease. and if a person wants to know about their life or wants to know about the changes arises in their lifestyle after this disease then he has to approach those persons who can further refer those individuals who can contribute to this study.in tis survey, snowball sampling is the best method.

Quota sampling:- it is also a non probability sampling method in which population is divided into subgroups which are mutually exclusive then the sample is drawn from that subgroups on the basis of given propotion. it is also known as the judgement sampling because in this sample items are drawn from the exclusive subgroups on the basis of investigator' personal judgement or his professional knowledge. the success of this method is totally dependent of investigator excellence of judgement.

in this firstly researcher divide the population of interest into groups of individuals who are similar in some ways then he determine the propotion of subgroup after that he chooses the size of sample and finally he choose the participants who will take part in the study.

advantages:- cost effective, easy to administer, less time consuming, account for proportion of population, useful method where probablity sampling methods can not be used,

disadvantages:- possibility of selection biasness, selection of sample is not random

for example;- an interviewer wants to interview 250 people in a certain geographical areas then he decides to interview 100 males, 100 females and 50 children. he selects a quota for each gender and after this with in these quota, on the basis of his personal experience or judgement he can select any of person for collecting the data.

investigator is interested to know the purchasing preferences of the customers of a particular local shopping plaza and he knows there is the differences in the purchasing prefeernces of males and females so he stratifies the population gender wise. then he finds the evidence that 60% of females are the customers fo this complex and he wants the sample size of 400 then he decides to research the 240 females which is the 60% of his total sample and 160 males. in this researcher did not prefer data randomly.