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Validity

Validity. For research to be considered valid, it must be based on fact or evidence; that is, it must be "capable of being justified.". Types of Validity. External validity is the extent to which results can be generalized to populations, situations, and conditions. Internal validity

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Validity

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  1. Validity • For research to be considered valid, it must be based on fact or evidence; that is, it must be "capable of being justified."

  2. Types of Validity External validity is the extent to which results can be generalized to populations, situations, and conditions. Internal validity is the extent to which results can be interpreted accurately.

  3. Internal Validity Requires: • random assignment of subjects to the test conditions. • the use of the same measurement instrument and procedures for all subjects.

  4. Eample #1: Internal Validity School 1 Teacher A Blue Program Class 1 8th Grade Boys Random Assignment Physical Performance Test B Administered by Teacher A 16 Weeks of Program Implementation Testing Period School 2 Teacher A Red Program Class 1 8th Grade Boys Random Assignment Physical Performance Test B Administered by Teacher A

  5. External Validity Requires: • Random selection of subjects (or random assignment to study conditions). • The use of a single measurement instrument and procedure.

  6. Example #2: External Validity Elementary School #1 15 Randomly Selected Teachers Survey Conducted Elementary School #2 15 Randomly Selected Teachers Results: All Teachers Schools 1-5 Elementary School #3 15 Randomly Selected Teachers Elementary School #4 15 Randomly Selected Teachers

  7. Reliability • Research is reliable to the extent that • (1) its components are consistent with one another (internal reliability) • (2) it can be replicated and yield similar outcomes (external reliability).

  8. Internal Reliability • Good internal reliabilityis demonstrated by a consistent: • data collection procedure, • data analysis process, and • interpretation of the data.

  9. Example #3: Internal Reliability Interviewer A Telephone Survey #1 28 randomly selected high school principals Interviewer B Telephone Survey #1 28 randomly selected high school principals Interviewer C Telephone Survey #1 28 randomly selected high school principals Interviewer D Telephone Survey #1 28 randomly selected high school principals

  10. External Reliability • Good external reliabilityexists when a study is described in enough detail to facilitate its replication. • A research report, if a study is to be considered externally reliable, includes: • detailed description of the study's design • detailed description of the population, sample & sampling strategy • explanation of the data collection strategy(ies) & procedure(s) • detailed explanation of analysis procedures. • Bottom Line: Can the study be replicated?

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