Psychometric Tests

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Psychometric Tests
2015-04-04 17:31:46
Psychology Psychometrics
Psychology,Individual Differences,Ability Testing
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  1. What is a constant?
    A value that does not differ
  2. What is a variable?
    A value that differs across individuals or conditions
  3. What is a discrete variable?
    A variable with a finite (or infinite if countable) range of values
  4. What is a dichotomous variable?
    • A type of discrete variable 
    • Can only assume 2 values (e.g. coin sides)
  5. What is a Polytomous variable
    • A type of discrete variable
    • More than 2 values
  6. What are continuous variables?
    • Variables with no theoretical limit 
    • Measured on scales which units can be infinitely subdivided 
    • Because of this we never get the true value, only an estimate
  7. What are nominal scales? Stevens (1946)
    • Numbers used as labels to identify a class so most used with categorical data (e.g. females=1, males=2)
    • All members of a particular set must be equal regardless of characteristics 
    • The numbers are only there to delineate categories so there is no point using them for stats tests apart from ratios using numbers in each category
  8. What are ordinal scales? Stevens (1946)
    • Same as nominal but also specify order 
    • No indication of difference between ranks, only their order 
    • Chiefly used for percentile scores 
    • Can be manipulated the same as normal data and non parametric tests can be carried out
  9. How do you convert a raw score into a percentile score?
    • Score- sample mean over sample standard deviation 
    • This gives us Z scores 
    • Z scores can be looked up in a distribution table
  10. What are interval scales? Stevens (1946)
    • The difference between two numbers reflects an equal distance in what is being measured
    • The 0 is arbitrary (0 for temp doesn't mean no temp)
    • This means ratios cannot be calculated as there is no true 0
  11. What is a ratio scale? Stevens (1946)
    • True zero and equal intervals 
    • Has the mathematical properties of identity, magnitude, equal intervals, and a true zero.
    • Used when measuring frequency of behaviour, time intervals and number of correct responses
  12. What are the limitations of ordinal scales?
    • Many scores are reported as %
    • Disrrivution in ranks is always greater at the extremes 
    • If you compared the 40th and 45th percentile the difference would be different than for the 90th and 95th
  13. What are the limitations of ratio IQ?
    • Stanford-Binet intelligence scale 
    • Ratio is calculate by dividing mental age on the SBIS with the actual age and dividing by 100
    • There are issues as chronological age rises steadily on a ratio scale, however mental age is ordinal