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Validity = accuracy of study Reliability = consistency of results - PowerPoint PPT Presentation


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Validity = accuracy of study Reliability = consistency of results. VALIDITY- Does your study reveal accurate and representative results?. Reliability. Is the measure able to give consistent measures over time?. Reliability checks?. Test-retest Split-half Inter-observer

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Validity = accuracy of study Reliability = consistency of results


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    1. Validity = accuracy of study Reliability = consistency of results

    2. VALIDITY- Does your study reveal accurate and representative results?

    3. Reliability • Is the measure able to give consistent measures over time?

    4. Reliability checks? • Test-retest • Split-half • Inter-observer • Convergence…replications

    5. VALIDITY- Does your study reveal accurate and representative results? • Internal Validity and External Validity • External Validity- generalizability • Issues • Sampling • Return rates • …..

    6. …External Validity • Generalizeability • Across population • Across environments • Across time

    7. Internal Validity

    8. Convergent validity • Different manipulations • Different measuring devices • Different populations…etc • Replication

    9. COMMON THREATS TO VALIDITY • Selection bias • random selection and assignment • Pretesting and matching • Recruitment technique

    10. History and Maturation Effects • Changes in the DV over time • Between pretest and post-test • Or between test sessions • constancy

    11. Mortality • Subject loss Over time • May reflect unintended effect of IV or DV • Subject loss may result in selection bias

    12. STOP FOR FUN! • ESP in PSYCHOLOGY?? • Somewhat critical • Lacking empirical validation • Should we remain open-minded? • Let’s give it a shot

    13. One of these symbols on each trial

    14. STOP until test complete

    15. What is Chance Performance? -1 out of 4 for each trial… -20 trials Chance performance = 5

    16. Just for fun let’s try again..this time seriously!

    17. answers

    18. Statistical Regression • Regression to the mean with repeated testing • Watch out for extreme scores..they may be due to chance

    19. Instrumentation • Changes in DV due to changes in measurement, not due to IV

    20. Sequence Effects-repeated testing effects • Practice effects • Test sensitization • Boredom/fatigue • Carry-over • Randomization and counterbalancing

    21. Subject Bias • Subjects can have attitude! RESPONSE SETS that produce inaccurate results • Soc desireability • Cooperitivity • Negativity • Volunteerism • -blindin-recruitment -deception or disguise lie detectors

    22. Experimentor Bias • Experimentors like to be correct! CONFIRMATIONAL BIAS • Demand characteristics • constancy • Automation • Double blinding

    23. How would you use blinding in a MJ drug study?

    24. PLACEBO EFFECTS ARE REAL • Expectation • What might someone expect MJ to do? • Beliefs/expectations can lead to real results….that are not related to the real effects of the IV.

    25. DOUBLE-BLIND PLACEBO CONTROL DESIGNS • Fake MJ?/ Ciggarette/ Pill other • Constancy • Can tease apart placebo effects from real drug effects.

    26. RANGE EFFECTS • Don’t forget the inability to see an affect of an IV on a DV does not necessarily mean there isn’t one. • Ceiling effects • Basement effects

    27. ULTIMATE CONTROL • Control procedures may be taylored for unique experiments • Ultimate control may never be completely achieved

    28. BEING A REAL PSYCHOLOGICAL SCIENTIST?? • The crux- identification of potential confounds • AND • RIVAL HYPOTHESIS

    29. RIVAL HYPOTHESIS • Alternative explanations for experimental results • Alternative to the research hypothesis

    30. Consider the following Hampton Court Maze

    31. The radial arm maze for rats

    32. Training of rats on the RAM • Initial freezing • Adaptation and exploration • Neophobia to food pellet • Adaptation to food • Rapid acquisition of task

    33. RAM memory errors? • Entrance into previously entered arm • One foot? Two? Half-way? All the way?

    34. Rats become quite good • Rarely make a memory error • Win-shift strategy

    35. Maybe they take an algorhythmic strategy • Right-right-right etc

    36. To control for strategies..forced choice procedures

    37. Using forced-choice procedures • No indication of algorhythm • Performance still very good

    38. SO… • What does rat performance in RAM show us?

    39. Rival Hypothesis? • Memory or sensory guidance? • Intra-maze or extramaze guidance? • Spatial memory or…..?

    40. Motivation-deficitsSensory-deficitsAttention-deficits