Test Theory (Subject) / Chapter 2 (Lesson)

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• inferences logical deductions about events that cannot be observed directly
• descriptive statistics methods used to provide a concise description of a collection of quantitative information
• inferential statistics methods used to make inferences from observations of a small group of people known as a sample to a larger group of individuals known as a population
• measurement application of rules for assigning numbers to objects
• properties of scales magnitude: the property of "moreness" equal intervals: if the difference between two points at any place on the scale has the same meaning as the difference beween two other points that differ by the same number of scale units absolute 0: when nothing of the property being measured exists
• types of scales                         magnitude                                  equal intervals               absolute 0  nominal               no                                                          no                              no ordinal               yes                                                        no                              no interval                 yes                                                     yes                               no ratio                     yes                                                     yes                               yes
• nominal scales really not scales at all; only purpose is to name objects no magnitude, no equal intervals, no absolute 0
• ordinal scale allows you to rank individuals or objects but not to say anything about the meaning of the differences between the ranks has magnitude, no equal interval, no absolute 0 e.g. rank classmates by height
• interval scale has magnitude, has equal intervals, no absolute 0 e.g. temperature
• ratio scale has magnitude, has equal intervals, has absolute 0 e.g. speed of travel
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• frequency distribution displays scores on a variable or a measure to reflect how frequently each value was obtained
• class interval the unit on the horizontal axis
• percentile rank what percent of the scores fall below a particular score (Xi)? B/N*100 B = number of scores below Xi N = total number of scores
• percentiles specific scores or points within a distribution; divide the total frequency for a set of observations into hundredths
• mean the arithmetic average score in a distribution
• variance the average squared deviation around the mean
• standard deviation the square root of the variance
• Z Score (Xi - Xbar)/S
• McCall's T T = 10Z + 50
• interquartile range bounded by the range of scores that represents the middle 50% of the distribution between 25th and 75th percentiles
• quartiles points that divide the frequency distribution into equal fourths
• deciles use points that mark 10% intervals
• stanine system converts any set of scores into a transformed scale, which ranges from 1 to 9
• norms refer to the performances by defined groups on particular tests
• tracking the tendency to stay at about the same level relative to one's peers
• norm-referenced test compares each person with a norm
• criterion-referenced test describes the specific types of skills, tasks, or knowledge that the test taker can demonstrate such as mathematical skills

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