Sampling Procedures Cs 12 Objectives Define Terms to Sampling Procedures Specify the advantages & disadvantage of Sampling Define the two approach of Sampling

Sampling Procedure: is the way the researcher select the elements to be investigated in the research study Terms Related to Sampling procedure Population: Entire set of elements, people, events, behaviors, substances, that could possibly be considered for the study Called Target Population, from which Sample was taken Element: Individual units of a population, can be a person, event, behavior, substance or any single measurement unit of a study An elements of a persons called SUBJECT

Terms Related to Sampling procedure Sampling Criteria: Standards or rules the researcher set up to determine what elements will be included in the population and sample (Characteristics of the Element) Sampling: Selecting a group of elements from total population which will be studied in the research (Process of Making a Selection) Sample: Group of elements selected from the total population to be studied in the research

Terms Related to Sampling procedure Randomization: Random selected of a representative sample from the target population, each sample has an equal opportunity to be chosen Randomly Sampling Frame: Listing every member of the target population according to sampling criteria to define a membership This listing called Sampling Frame

Terms Related to Sampling procedure Accessible Population: Random Selection is ideal, Time & Coast factors limited the possibility of achieving realistic & idealistic An accessible population is the portion of the target population to which the researcher has reasonable access Sample should be obtain from the accessible population Representative: Sample must be like the target population as many way of possible in relation to variables to be examined & other factors influenced the study variables

Advantage of Sampling Economic & Efficient to work with small group of elements, does not require many resources Possible to obtain reasonable accurate information

Disadvantages of Sampling Sampling Bias refers to the systemic overrepresentation or underrepresentation of some segment of population in term of characteristic relevant to research question Sampling Error

Approaches to Sampling Reason to chose sampling approach: To decrease Systemic bias To decrease sampling error To increase representativeness

Approaches to Sampling Probability Sampling Nonprobability Sampling

Probability Sampling Probability: fact that every member (element) of the population has a probability higher than zero of being selected for the sample refereed as a Random Sampling To obtain a Probability Researcher must:- know every element in the population Develop A Sampling Frame Clearly define the population

Researcher Must have knowledge about each Strata Probability Sampling Simple Random Sampling: Elements are selected from the frame randomly Stratified Random Sampling: First population is divided into two or more Strata or Subgroups to achieve representativeness Such as: divided according to Age, Race, Gender Socioeconomic Status Diagnosis Researcher Must have knowledge about each Strata

NonProbability Sampling Characteristics Not every element of population has an opportunity for selection in a sample No Sampling Frame Parameters of population may not be known No clearly identification for population Hypothetically population is defined

NonProbability Sampling Accidental Sampling: Convenience Sampling or Incidental Sampling Subject included in the study because they happened to be in the right place at the right time To avoid Multiple biases strategies may be used In expensive Accessible Require less time More easy than probability

NonProbability Sampling 2. Quota Sampling: Use an accidental sampling technique with an added feature a strategies to ensure the inclusion of a subject types that are likely to be underrepresentative in the accidental type Offers an improvement on accidental type To decrease the biases

NonProbability Sampling 3. Purposive Sampling: Judgmental Sampling Conscious Selection of a certain sample to be studied Depend on the Precision of the researcher's judgment

Sample Size General Rules to select Sample Size Make Size as LARGE as possible Factors should be considered in making decision about sample size:- Type of the study Number of Variables Sensitivity of the measurement tools Data analysis techniques Expected effect size