1. Statistical Sampling in Audit for the NSO Comptroller & Auditor General of India 1 Introduction to Statistical Sampling

2. Statistical Sampling in Audit for the NSO Comptroller & Auditor General of India 2 A sample is a group of units selected from larger group (the population). By studying the sample one hopes to draw valid conclusion about the population.It may be statistical or nonstatistical. What is a sample ?

3. Comptroller & Auditor General of India 3 What is Statistical Sampling ? The essential features of statistical sampling are: 1) The sample units (or transactions) should have a known probability of selection. 2) The sample result should be evaluated mathematically, that is in accordance with probability theory.

4. Comptroller & Auditor General of India 4 Advantages of Statistical Sampling  The sample results are objective and defensible as it is free from any kind of bias.  The method provides a means of advance estimate of sample size.  The method provides an estimate of the sampling error.  It can save time & money.  Statistical samples may be combined and evaluated, even though accomplished by different auditors.

5. Comptroller & Auditor General of India 5 Two broad categories of Statistical Sampling  In attribute sampling one selects the sampling unit randomly to estimate number of time an event occur in the population.It answer the question, How many ?  In variable sampling one selects the sampling the sampling unit randomly to estimate population average or total.It answer the question, How much?

6. Comptroller & Auditor General of India 6 Sampling vs. Non-sampling error  Sampling error is generated due to failure of selecting the representative sample.It is measurable under statistical sampling.  Non-sampling error is generated due to failure of measurement of true characteristic(s).Which may be due to, i) non-response ii) measurement error iii)fatigue & iv)others.which can be controlled my better training & management etc.There is no standard procedure to measure this error.

7. Comptroller & Auditor General of India 7 Types of Statistical Sampling  Simple Random Sampling  Systematic Random Sampling  Probability Proportional to Size  Monetary Unit Sampling  Stratified Sampling  Cluster sampling  Multistage Sampling

8. Comptroller & Auditor General of India 8 The principal steps in auditing using statistical sampling :  Objective  Population definition  Degree of precision desired  The Sampling Frame  Selection of samples  Preparation of Questionnaires/Data Format  Audit of selected units.  Recoding of audit observation in the prescribed data format  Statistical evaluation of survey results  Report writing

9. Statistical Sampling in Audit for the NSO Comptroller & Auditor General of India 9 Any Questions ?