PR

• Sampling


  The process of systematically selecting individuals, units or groups to be analyzed during the conduct of study
• Generalizability

  The extent your findings can be applied in other contexts
• Sampling errors

  Differences between what is present in a population and what is present in a sample

  
• Determining sample size

  1. Use a formula (Slovin's formula)

  2. Use a table for sampling size calculation

  3. Use heuristics

  4. Conduct a literature review

  
• Find out what sample of a population of 1,000 people you need to take for a survey on their soft drinks preferences using Slovin's formula
• Compute sample sizes for the following populations

  1. 48

  2. 98

  3. 275

  4. 893

  5. 1082

  
• Probability sampling


  Everyone has an equal chance of being selected
• Probability sampling procedures


  • Simple random sampling
  • Systematic sampling
  • Stratified random sampling
  • Cluster sampling
  • Multi-stage sampling

  
• Validity


  Are you actually measuring what you want to measure?
• Face validity


  The test appears to measure the variables being studied
• Face validity


  • A mathematical test consisting of problems in which the test taker has to add and subtract numbers
  • A questionnaire on algebra proficiency with unsuitable content, irrelevant questions, unclear language, and inconsistent formatting
• Content validity


  Assessment whether a test (items/questions) is representative of all aspects of the construct (no missing aspect)
• Content validity


  • An English proficiency test with questions covering listening, reading, writing, and speaking
  • A questionnaire with better content validity by ensuring all items are relevant to the construct it aims to measure
• Criterion validity


  The extent to which scores on an inventory or scale correlate with external, non-test criteria
• Criterion validity


  • A new English writing ability test is compared to an existing valid test of English writing ability
  • Pre-employment tests are validated by correlating test scores with future career success
• Construct validity


  The instrument is able to detect what should exist theoretically
• Measuring construct validity


  Group comparison - identify two groups, one experiencing the construct and one not, then run a t-test to see if there is a significant difference
• Reliability


  The extent to which a scale produces consistent results if the measurements are repeated a number of times
• Types of reliability


  • Test-retest reliability
  • Interrater reliability
  • Parallel forms reliability
  • Internal consistency reliability
• Ideation


  The formation of ideas or concepts
• Construct validity

  • Should be demonstrated empirically
• Types of validity


  • Face validity
  • Content validity
  • Construct validity
  • Criterion validity
• Measuring construct validity


  1. Group comparison

  2. Identify two groups

  3. Administer test to both groups

  4. Run t-test for two independent samples
• There should be a significant difference between the two groups
• Stages of stress


  • Alarm
  • Resistance
  • Exhaustion
• Reliability


  Refers to the extent to which a scale produces consistent results, if the measurements are repeated a number of times
• Types of reliability


  • Test-retest reliability
  • Interrater reliability
  • Parallel forms reliability
  • Internal consistency reliability
• Test-retest reliability


  Consistency of results over time
• Interrater reliability


  Consistency of agreement among people
• Parallel forms reliability

  Consistency of equivalent versions of a test
• Internal consistency reliability


  Consistent correlation between items belonging to one construct
• Methods of measuring internal consistency reliability

  • Split-half coefficient
  • Cronbach's alpha
  • Kuder-Richardson 20 or 21
• At the end of the discussion, the students should be able to: construct an instrument and establish its validity and reliability; describe the intervention, if applicable; plan the data collection and the data analysis; present a written methodology
• Instrument


  A measurement device or tool (survey, test, questionnaire, etc.)
• Data collection procedures


  • Survey
  • Observation
  • Interview
• Types of interviews


  • Structured
  • Nondirective
  • Unstructured
  • Focus
• Steps in collecting data

  1. Select your sample

  2. Send advance notification letter

  3. Make initial contact

  4. Screen and obtain consent

  5. Collect data
• Data analysis procedures


  • Descriptive analyses
  • Inferential analyses
• Descriptive statistics

  • Frequency
  • Percentage
  • Rank
  • Variability
  • Central tendency (mean, standard deviation)
• Inferential statistics


  • Significant differences (t-test, ANOVA)
  • Chi-square