WHAT IS RELIABILITY IN STATISTICS

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What is reliability in statistics with example in SPSS



    What is reliability ?

  • Extent to which results are consistent
  • Validity is the extent to which the instrument measures what it claims to measure.
  • A good measurement instrument is both reliable and valid.
  • Reliability is a prerequisite for validity.


    Ways to measure Reliability:

  1. Test – Retest
  2. Parallel forms
  3. Split-half method
  4. Internal consistency


    Interpreting Test – Retest and Parallel Forms                 Reliability: 

  1. Measured with correlation coefficient between halves or between tests.
  2. Generally an range of 7-8 is considered good reliability, but it depends on what else is available.


    Split – half Method:

A method of determining the reliability of a test by dividing the whole test into two halves and scoring the two halves separately.


    Inter – rater reliability:

  • It as the name indicates relates to the measure of sets of results obtained by different assessors using same methods.
  • Benefits and importance of assessing inter-rater reliability can be explained by referring to subjectivity of assessments.


    Internal Consistency Reliability:

  1. Consistency of items within a measurement instrument.
  2. Split-half-divide test items into two groups and obtain a score for each half : correlate the scores.
  3. Cronbach’s alpha – average of all possible split half estimates.


    Assumptions:

  • Equivalent halves or items.
  • Unrelated measurement errors between halves or items.
  • Items represent the same underlying factor.
  • Items have been transformed if necessary.


    CRONBACH’S ALPHA:

Reliability refers to whether your data collection techniques and analytic procedures would reproduce consistent findings if they were repeated on another occasion or if they were replicated by another researcher.


    A commonly accepted rule:


this is the main rule of Cronbach's alpha value to accept the questionnaires


Steps in SPSS Software:












NOTE:
                        Anxiety- (Q1 - Q5)      / Alpha value is 0.873
                        STRESS-(Q6 - Q9)     / Alpha value is 0.615

    Reliability (Cronbach’s Alpha)- Interpretation:

The Cronbach’s Alpha value of the anxiety benefits is 0.873 which is more than 0.7. hence the reliability of the question is proved. The Cronbach’s Alpha value of the stress benefits is  0.615 which is more than 0.6. hence the reliability of the question is proved i.e.., the questionnaire is reliable for the purpose of data collection.


    FOR MORE TEST STATISTICS ( CLICK )




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