Card Set Information

2011-10-13 22:49:34
statistics vocab

For my psychometrics Quiz
Show Answers:

  1. What are the 4 Scale of Measurement?
    Nominal, Ordinal, Interval, Ratio
  2. Nominal Scale of Measurement
    Classify, No logical order
  3. Ordinal Scale of Measurement
    Classify and rank or order
  4. Interval Scale of Measurement
    Classify, orders, adds zero (arbitrary) and equal units
  5. Ratio Scales of Measurement
    Classify, order, equal units, true zero point

    True Ratio
  6. Why not use raw scores?
    Lack of comparability, original score of 30 could mean several things, need to change it into something with a meaningful value such as a derived score
  7. Examples of Derived Scores
    Age/Grade equivalents, perventile ranks, standard scores
  8. Name two types of Developmental Scores
    Age Equivalent Scores

    Grade Equivalent Scores
  9. What are some problems with age and grade scores?
    Different Meaning:Raw scores can mean several different things


    Meaningful Difference: Most tests don't have enough items at a specific age grade level

    Ordinal Scale: Can't get standard error of measurement

    Imply constant rate of growth: unequal intervals

    Imply false standard

    Different meanings across tests
  10. What are Percentiles?
    Not percentage correct, as high or higher than xx% of children on this test (not as well or better), among easiest to interpret for parents, not useful for comparing scores (overestimate differences in center of normal curve and underestimate differences on tails)
  11. Why are percentiles not useful in comparing scores?
    They overestimate differences in the center of the normal curve and underestimate difference on the tails of the normal curve
  12. What are standard scores?
    They make use of means and standard deviations, derived from z-scores, best scores for comparing
  13. What are z-scores? What is the formula?
    Z-scores are the number of SD's from the mean, easy to convert from z-scores to others

    Z scores = (Raw-Mean)/Standard Deviation
  14. T-Scores
    • Mean = 50
    • Standard Deviation = 10
  15. What are norm referenced tests?
    Tests that compare score to a normative sampe, must control variables that are likely to affect variable meausuring.
  16. What is a normative sample?
    A representative sample that matches the population. Larger size means more stability. Relevance of Comparisons.
  17. M=
  18. SD=
    Standard Deviation
  19. SEM=
    SEM=Standard Error of Meausrement
  20. Central Tendency
    Mean, some include mode and median
  21. Variation (Scatter)
    Standard Deviation, Variance, some include Range
  22. Name the four types of notation.
    Central Tendency, Variation (Scatter), Standard Error of Measurement, Correlation =r
  23. Name ways to summarize data for a single variable.
    Charts, graphs (histograms), central tendency, variabiltiy
  24. What is a histogram? Name its different parts.
    Histogram (history of data) = Bar Graph

    • Vertical Bars=data, frequency
    • Baseline (horizontal axis)=observed scores on the dependent variable
  25. What is a frequency polygon? Name its parts.
    Frequency Polygon = Line Graph

    Vertical lines = score intervals, individual scores

    Baseline (horizontal axis) = frequencies or percentages
  26. Skew
    Positive scew: has a longer tail on the higher scores or right side

    Negative scew: has a longer tail on the lower scores or left side
  27. Kurtosis
    Playukurtic Curve (very low and wide)

    Leptokutic Curve (very high and narrow)
  28. What is a tendency
    A data trend
  29. Name two types of trends.
    Measures of central Tendency, Measures of dispersion (spread or variability)
  30. What are types of central tendency measures?
    Median Mean Mode
  31. What are measures of dispersion?
    Measures of variability = range, variance, and standard deviation
  32. What is mode?
    The number that appears most often
  33. What is the median? And how do you calculate it?
    The middle score, 1/2 below and 1/2 above, put data in order and find the middle one, if you have an even number you add the middle two numbers and divide by two
  34. How do you find the mean?
    Add up all of the scores and divide by the number of scores
  35. Differences in Distributions:
    Where are the median, mode, and mean in:
    a symmetrical distribution?
    a positively skewed distribution?
    a negatively skewed distribution?
    Symmetrical Distribution: All line up in the middle

    Positive Skew (Left to right): Mode, Median, Mean

    Negative Skew (Left to right): Mean, Median, Mode
  36. Measures of Variability
    how spread out the scores are, measures of variability cannot be negative, suggests dispersion
  37. What are Homogeneous Scores?
    Little variability
  38. What are heterogeneous scores?
    High Variability
  39. What is range?
    the difference between the lowest and the highest
  40. What is interquartile range?
    Spread among middle 50% of scores
  41. Name the measures of variability.
    Range, Interquartile Range, Variance, Standard Deviation
  42. What is variance? How do you calculate it?
    Variance is how much scores deviate from the mean (used more in statistics and less in measurement), average of the squared deviation scores
  43. What is Standard Deviation? How do you Calculate it?
    • SD is another measure of dispersion
    • SD=square root of variance
    • SD puts scores back in original metric
    • Useful for describing scores, inherent in any type of standard scores,
  44. What is a normal curve?
    A normal curve is a unimodal, symmetrical graphic depiction of scores
  45. How do you summarize data on more than one variable?
    Bivariate relations, correlations
  46. What is a correlation?