Sampling
- 2. DEPARTMENT OF COMPUTER SCIENCE AND SOFTWARE ENGINEERING MISS RABIYA
- 3. SAMPLING Presented to : ma’am Rabbia
- 4. PRESENTED BY: LAIBA BATOOL 3095 RIMSHA QAISER 3112 HIRA BARLAS 3126 QANDEEL ZAINAB 3080 TANIA RASHID 3056
- 5. SAMPLING Statistical procedure Concerned with the selection of individual observation Helps to make statistical inference about population Process of choosing a representative sample from target population
- 6. SAMPLING Sampling is of two types Probability sampling Non probability sampling It should not be confused with sample
- 7. PURPOSE OF SAMPLING To understand the population To gather data about the population To accurately describe the parameters of population To save time and money To estimate some indicator To identify participants
- 9. Probability Sampling • Every unit has equal chance being selected for sample • Random Sampling • Drawing names from hat or choosing the short straw Types Of Probability Sampling 1.Simple Random Sampling 2.Systematic Random Sampling 3.Stratified Random Sampling 4.Cluster Random Sampling 5.Multi-stage Random Sampling
- 10. 3. Stratified Random Sampling • Population is divided in two or more groups called strata • A sample is selected from each stratum Types of Stratified Random Sampling • Proportionate Stratification • Disproportionate Stratification 4. Cluster Random Sampling • Population divided to subgroups (“clusters”) • A simple random sample is taken • Used when population is too large
- 11. 1. Simple Random Sampling • Get a list of “sample frame” • Generate random numbers • Select one unit per random number 2.Systematic Random Sampling • Order all units in sampling frame • Select the kth unit
- 12. 5.Multi-stage Sampling • Combination of all types • Involve selecting a sample in at least two stages I. Systematic and Stratified II. Cluster and Simple Random
- 13. NON- PROBABILITY SAMPLING Non Probability sample method in which some elements of population have no chance of selection Types Convenience sampling Snowball sampling Purposive sampling Quota sampling
- 14. 1) Convenience Sampling A type of sampling where the element selection is based on ease of accessibility 2) Snowball Sampling The research starts from the key person and introduce the next one to become a chain
- 15. 3) Purposive sampling The sample based on his or her judgment about some appropriate characteristics required of the sample member 4)Quota sampling In Quota sampling, a population is first segmented into mutually exclusive sub groups, just as in stratified sampling
- 17. ADVANTAGES OF SAMPLING: • Low cost of sampling. • Less time consumed in sampling. • Much easier to collect information. • Accuracy of data is high. • Suitable in limited resources.
- 18. DISADVAN TAGES OF SAMPLING: • Chances of biasness. • Difficulties in selecting a truly representative sample. • In adequate in the subject. • Impossibility knowledge of sampling. • Changeability of unit.
- 19. Sampling Errors
- 20. Sampling Errors The errors which arise due to the use of sampling surveys are known as sampling errors. Types of sampling errors Biased errors: due to selection of sampling techniques, size of the sample. Unbiased errors/ Random sampling errors: difference between the members of the population included or not included Increasing the sample size will reduce this type of error
- 21. Non Sampling Errors Due to sample observations being selected improperly Types of non sampling error: Errors in data acquisition Due to incorrect measurement being taken Inaccurate recording of data Non response error When units selected as part of the sampling procedure do not respond in wkole or in part Selection bias when some members of target population cannot possibly selected for inclusion in sample Increasing the sample size will not reduce this type of error
- 22. YOU CAN’T LEARN UNTILL YOU QUESTION IT !