Sampling continued

Size of sample- factors to be considered1. The size of the universe2. The resources available3. The degree of accuracy or precision

desired4. Homogeneity or heterogeneity of the

universe5. Nature of study6. Method of sampling adopted7. Nature of respondents

Merits of sampling1. Less time consuming2. Less cost3. More reliable results4. More detailed information5. Sampling method6. To judge the accuracy of the

information on a census basis

Limitations1. Carefully planned 2. It requires the services of experts3. Complicated sampling plan4. When complete information is required

Sampling and Non Sampling errors1. Sampling errorsa. Biased errorsb. Unbiased errors

Causes for bias1. Faulty process of selectionLeads to bias such as- Deliberate selection Conscious or unconscious bias Substitution Non response Appeal to vanity2. Bias due to faulty selection of data3. Bias of analysis

b.Unbiased errorsThese errors arise due to chance differences between the members of population included in the sample and those not included. Cumulative or non compensating error Non cumulative or compensating error.

Methods of reducing sampling errors

Non-sampling errors1.Defective problem definition.

2.Defective population definition

3.Frame error

4.Surrogate information error

5.Non response error

6.Measurement error

7.Experimental error

8.Poor questionnaire design

9.Interviewer bias

10.Data processing error Coding error Recording error

11.Data analysis error Summation Division Application of wrong statistical

techniques

12.Interpretation error