Questions to ask about tests scores 1. Do each of these numbers actually conveys quantitative information? (scales of measurements)
Properties of ScalesMAGNITUDE: the property of “moreness.” A scale has the property of magnitude if we can say that a particular instance of the attribute represents more, less or equal amounts of the given property than does the another instance.
EQUAL INTERVALS A scale has the property of equal intervals if the difference between 2 points at any place on the scale has the same meaning as the difference between 2 other points that differ by the same number of scale units.
ABSOLUTE ZERO An absolute zero is obtained when nothing of the property being measured exists.
Types of Scales1. Nominal Scales are really not scales at all, their only purpose is TO NAME OBJECTS. Nominal scales are used when the information is qualitative rather than quantitative.
2. A scale with the property of magnitude but not equal intervals or an absolute 0 is an ordinal scale. For most problems in Psychology, the precision to measure the exact differences between intervals does not exist. So most often, one must use ordinal scales of measurement.
3. When a scale has the properties of magnitude and equal intervals but not an absolute 0, it is an interval scale.
4. A scale that has all three properties (magnitude, equal intervals and absolute 0) is called a ratio scale.
1. Which of the following is least likely to be a variableamong persons in a Testing class?a) socio-economic status f) speaking abilityb) typing speed g) favorite foodc) nationality h) musical abilityd) assertiveness i) year of birthe) religious affiliation j) age2. Which three variables in Question 1 would most likely bemeasured in nominal scale?3. Which option in Question 1 best illustrates an interval butnot a ratio scale?4. Which two variables in Question 1 are most likely to bemeasured by ratio scales?
2. What is the basic pattern of the set of tests scores? How do they “run”? What do they “look” like? (simple ways of tabulating and graphing a set of scores)
What is the basic pattern of the set of tests scores?Frequency Distribution: a display that shows how often each score has occurred.Grouped Frequency Distribution: a fairly compact table illustrating how many people there are in each score interval.Cumulative Frequency Distributions: how many people got scores below some particular values.
3. What is the group like on the average? In general, have they done as well on the test as some other groups of examinees? What is the typical level of performance in the group? (middle score statistic to represent the average or typical score)
1. Mean: the arithmetic average score in a distribution. To calculate the mean, we total the scores and divide the sum by the number of cases, or N.
4. To decribe the extent to which the scores spread out away from the average value— (measures of variability)
5. How does this person stand relative to the group? (how a particular individual stands on one of the tests score)
6. To what extent do those who excel in Reading also excel in Mathematics? To what extent do these two abilities go together in the same individuals? (correlation)