L>LOL two Plus Two equates to Four, but Not AlwaysA line ON LIFE UnpublishedTwo amounts to Four,But no AlwaysDavid A. Gershaw,Ph.D.Believe it or not, periodically 2 + 2 does no equal 4. It relies on what type of measurement scale you space using. There are four species of measurement scales � nominal, ordinal, interval, and also ratio. Only in the last 2 categories go 2 + 2 = 4. Allow me explain.All the nominal scale does is name or classify. Every number just represents a classification or individual. Because that example, number on baseball or football uniforms are just nominal. Having actually the number "1" on her uniform does no necessarily median you room "numero uno" (the best) in your sport. Social defense numbers are likewise nominal. All they perform is name or share the individual.The ordinal scale has all the attributes of the nominal range plus the ability to rank objects follow to some attribute. If girlfriend ranked every the members the a team according come height, "1" would be the tallest, "2" the 2nd tallest and also so on. However, the intervals between these rankings room not necessarily equal. If the tallest civilization were 5"11", 5"8" and 5"7", respectively, the interval in between the an initial two ranks would certainly be 3 inches, if the interval in between the last 2 is only 1 inch. Ranking in miscellaneous sports and also beauty contests are likewise only ordinal scales.An interval scale combines the characteristics of the vault scales v equal intervals. The ideal example would be a centigrade (Celcius) thermometer. The readjust in heat between 0oC and also 10oC is the same as between 10oC and 20oC. Yet watch out! 20oC is not twice as warm as 10oC! Why? expression scales have arbitrary zeros (just since we decided to call it zero), fairly than pure (true) zeros. At 0oC water freezes, however that go not average that there is no heat.In contrast, the proportion scale has all the characteristics of the previous scale plus an absolute (true) zero, just like a Kelvin thermometer. in ~ 0oK, theoretically over there is no heat. You have actually nothing that what you are measuring, as such the zero is true or absolute. However, 0oK = -273oC. Because one level indicates the exact same heat adjust in both scales, we have the right to see what happens once we to compare them.20oC = 293oK10oC = 283oK0oC = 273oK-273oC = 0oKThus 20oC is no twice as warm as 10oC! return this might seem confusing, the becomes really clear as soon as you switch to the Kelvin range � 293oK absolutely does not also look choose it is twice as hot as 283oK. Only with a proportion scale � with a true zero � can you effectively use the ide of multiples. Length, height, and weight are ratio scales. Therefore, you can correctly say the "A yard is 3 times longer than a foot" or "A 200-pound male weighs twice as much as a 100-pound woman."If you are having actually some trouble expertise this, it is probably because most that you have actually only offered ratio scale in school. Mathematics courses typically deal only with scale that have actually true zeros and also equal intervals.How does this relate to psychology? many psychological tests are just ordinal measures! Let"s to speak that 3 different civilization score 60, 40 and 20 ~ above a test of extraversion (having outgoing personality traits). Since it is an ordinal scale we have the right to correctly say the 60 is the many extraverted (rank #1), 40 is the second most, and also 20 is the third most or least extraverted. Notification that the difference between 60 and also 40 is 20, and the difference in between 40 and 20 is additionally 20. However, a 20-point distinction in one part of the scale may not have the same definition as a 20-point difference in another component of the scale. Therefore the same difference of 20 points might not reflect the very same underlying distinction in extraversion, because we don"t recognize if the intervals space equal. That is not an interval scale.Likewise, even though 20 x 2 = 40 and also 20 x 3 = 60, we cannot effectively say the the human being with a score that 60 has actually three time the extraversion together the person with 20 or that the person with a score of 40 has actually twice together much. We cannot compare scores in regards to multiples, since the scale has no true or pure zero. That is no a proportion scale.Again, most psychological test � and virtually all tests provided in our colleges (including mine) � are only ordinal measures. These tests enable ranking of world according come various attributes � personality properties or expertise in details subject areas.

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However, if someone it s okay a score double as great as yours, that does not mean that person knows twice as much as girlfriend do.Go earlier to "A heat on Life"page.