Planning Research Part 1 Method, Participants, Instruments & Ethics Kathy-ann Hernandez, Ph. D. Spring 2007

Participant Selection Whom to select? How to select? How many to select?

Sampling Terms Random sampling/Probability Every individual in the population of interest has an equal chance of being in the sample Biased sampling/Non Probability some individuals from the population of interest have a greater chance of being selected than other individuals

Sampling Procedures Probability/Random Physical Mixing Process Random Number Table Systematic Random Sampling Non-probability Sampling/non random sampling Convenience or Accidental Sampling Purposive sampling Biased Sampling

QL and QN Sampling Procedures Quantitative Methods Simple Random Sampling Stratified Random Sampling Systematic sampling Cluster Sampling Qualitative Methods Purposive sampling Criterion sampling Convenience Sampling

Population vs Sample Select by physically mixing or use table of random numbers

Stratified Sampling Stratified random sampling used when we have subgroups in our population that are likely to differ substantially behavior. Create separate strata and select randomly from each stratum. (gender, age groupings)

Stratified Proportionate Sampling Proportionate sampling can be used with stratified sampling. Select individuals from each stratum based on the proportion they comprise of the population. Ex. 400 (M) ; 500 (F) - select 10% from each group.

Systematic Sampling Select every nth person

Cluster Sampling Cluster sampling is useful when it would be impossible or impractical to identify every person in the sample. Instead of sampling 10% of EU students, sample 10 % of the classes randomly.

Non probability/non random sampling Convenience or Accidental Selecting a sample because it is easily accessible and reasonably representative of the population of interest. Purposive Sampling Handpicked individuals because they have characteristics of interest Criterion Sampling Clear criteria established for identifying participants

Convenience Sampling

Looks like cluster sampling, but clusters are not selected at random

Purposive Sampling Purposive sampling targets a particular group of people.

Types of Purposive Sampling Random Purposive Sampling Case sampling Typical and extreme or deviant Intensity sampling Maximum Variation sampling Homogenous sampling Opportunistic sampling Stratified Purposive sampling Snowball sampling

Instrumentation How do I measure my variable of interest? Where can I find instruments? Can I create an instrument?

Instruments Use instruments used in Previous Research Locate instruments from databases ETS Tests in Print Buros Mental Measurement Yearbook Begin thinking about creating your own instrument

Issues in Devising New Instruments QN Validity- accuracy Judgmental, criterion-related, and construct validity Reliability- consistency Number of items, correlation coefficients QL Credibility – accuracy member checks; triangulation of sources Dependability – control of subjectivity Triangulation of instruments Handout