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Research In Management

Research In Management. Class 5 Sampling Theory And Methods. Objectives. Explain the role of sampling in the research process Distinguish between probability and non probability sampling Understand factors to consider when determining sample size

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Research In Management

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  1. Research In Management Class 5 Sampling Theory And Methods

  2. Objectives • Explain the role of sampling in the research process • Distinguish between probability and non probability sampling • Understand factors to consider when determining sample size • Understand the steps in developing a sampling plan

  3. Sampling • Sample is a smaller group, which is selected from the population to be observed and included in the research. • Selection of a small number of elements from a larger group, results of which are drawn from the sample and generalized to the larger group • Census • Sampling

  4. Role of sampling • Identifying, developing, and understanding new constructs that need to be investigated • Plays an indirect role in the design of the questionnaire • Enables the researchers to make decisions using limited information

  5. Basic Sampling Theory • Population: defined target population • Sampling units: the target population elements available for selection during the sampling process • Sampling frame: list of all eligible sampling units • Elements: • Must be unique • Must be countable • Summed to make target population • Identify correctly

  6. Types of Error • Sampling Error • Any type of bias that is attributable to mistakes in either drawing a sample or determining sample size • Non Sampling Error • A bias that occurs in a research study regardless of whether a sample or census is used

  7. Types of sampling • Probability sampling: In probability sampling, every individual in the population has a non-zero chance to be included in the sample of the study. • Non probability sampling: In non probability sampling the sample is not selected randomly. It is used where the population is widely spread and it is difficult to use any sampling frame for such a great population. Based on the judgment of researcher.

  8. Types of sampling • Probability sampling 1. Simple Random Sampling 2. Stratified Sampling 3. Cluster Sampling 4. Systematic Sampling • Non probability sampling 1. Convenience Sampling 2. Judgment Sampling 3. Quota Sampling 4. Snowball Sampling

  9. Comparing Probability and Non probability Sampling Methods

  10. Sample Size Factors in Determining Sample Sizes • Variability of the population characteristic under investigation • Level of confidence desired in the estimate • Degree of precision desired in estimating the population characteristic

  11. Sample Size Estimates • When estimating a population mean n = (ZB,CL)(σ/e) 2 • When estimates of a population proportion are of concern n = (Z2B,CL)([P x Q]/e2)

  12. Considerations • Direct relationship between the desired CL (90%, 95%, 99%) and the require sample size • Acceptable tolerance level of error—amount of precision desired (2%, 5%, or 10%)

  13. Sample Size • Researchers can estimate the number of sampling units that must be surveyed • Not all initial responses are usable • Inactive mailing addresses • Telephone number no longer in service • Incomplete responses • Factors to consider in drawing a sample • Reachable rate • Who is qualified to be included in the survey • Expected completion rate

  14. Critical Factors for Sample Design • Research Objectives • Degree of accuracy • Resources • Time Frame • Knowledge of target population • Scope of research • Statistical analysis needs

  15. Sampling Plan Steps • Define the Target Population • Select the Data Collection Method • Identify the Sampling Frame(s) Needed • Select the Appropriate Sampling Method • Determine Necessary Sample Size and Overall Contact Rates • Create an Operating Plan for Selecting Sampling Units • Execute the Operational Plan

  16. Four commonly used confidence levels and Zα/2 1-ααα/2 Zα/2 .90 .10 .05 1.645 .95 .05 .025 1.96 .98 .02 .01 2.33 .99 .01 .005 2.575

  17. Discussion Questions • Determine the sample size required to estimate a population mean to with in 10 units given that the population standard deviation is 50. A confidence level of 90% is judged to be appropriate. • A statistics practitioner would like to estimate a population mean with an error of 10 units. The confidence level has been set at 95% and σ=200. Determine the sample size.

  18. Announcement • Proposals for group work are due in the next class • Don’t worry if you are unable to find a supervisor. Its not mandatory.

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