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Sampling Process: Steps, Methods, and Characteristics

Learn about the steps, methods, and characteristics of the sampling process to obtain information from a sample of a larger population.

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Sampling Process: Steps, Methods, and Characteristics

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  1. SAMPLING Professor Dr.Ali Al-Juboori

  2. STEPS IN SAMPLING PROCESS STEP 1: Define the target population STEP 2: Identify the sampling frame STEP 3: Specifying the sampling unit. STEP 4: Selection of the sampling method. STEP 5: Determination of sample size. STEP 6: Specifying the sampling plan. STEP 7: Selecting the sample

  3. Sampling is the process of obtaining information from a sample of a larger group (population). • A sample is “a smaller (but hopefully representative) collection of units from a population used to determine truths about that population”.

  4. Characteristics of Good Samples : • Representative • Accessible • Low cost

  5. Select “sample units” • Individuals • Household • Streets • Telephone numbers • Companies

  6. *Selecting a sampling design or procedure: • PROBABILITY • NON- PROBABILITY • *Determine the sample size.

  7. Probability sampling - equal chance • of being included in the sample (random) • -simple random sampling • -systematic sampling • -stratified sampling • -cluster sampling • Non-probability sampling - unequal chance of being included in the sample (non-random) • -convenience sampling • -judgment sampling • -snowball sampling • -quota sampling

  8. PROBABILITY SAMPLING

  9. Simple RANDOM SAMPLING A sampling procedure in which every element in the population has a known and equal chance of being selected as a subject (e.g., drawing names out of a hat).

  10. SYSTEMATIC SAMPLING If a sample size of n is desired from a population containing N elements, we might sample one element for every n/N elements in the population.

  11. STRATIFIED SAMPLINGطبقية It is the process of segregating the population into groups and select by systematic sampling method from each strata or cell.

  12. CLUSTER SAMPLING: عنقودية The population is divided into clusters like families and then simple random sampling is applied.

  13. NON - PROBABILITY SAMPLING

  14. CONVENIENCE SAMPLING • Sometimes known as or opportunity sampling or accidental or haphazard sampling. • A type of non probability sampling which involves the sample being drawn from that part of the population which is close to hand. That is, readily available and convenient.

  15. JUDGMENTAL SAMPLING • The researchers choose the sample based on who they think would be appropriate for the study. • This is used primarily when there is a limited number of people that have expertise in the area being researched.

  16. SNOWBALL SAMPLING • Selection of additional respondents is based on referrals from the initial respondents ( friends of friends) • Used to sample from low incidence or rare populations.

  17. QUOTA SAMPLING • Quota sampling is a method for selecting survey participants. A researcher gathers data from individuals possessing يمتلكون identified characteristics and quotas. حصص For example, an interviewer may be told to sample 200 females and 300 males between the age of 45 and 60.

  18. Threats to Valid Sampling • The population you want to generalize to is different from your sample • The setting/place you want to generalize to is different from the place you conducted your study • The time when you conducted your study was unsuitable

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