2 The test construction process Defining the TestSelecting Scaling MethodConstructing the itemsTesting the itemsRevising the testPublishing the test
3 Defining the TestExplain the test purpose explicitly and propose a fresh focus for what the test intend to measure, for example, intelligence.K-ABC
4 Selecting Scaling Method The immediate purpose of psychological testing is to assign numbers to responses on a test so that the examinee can be judged to have more or less of the characteristic measured.Levels of Measurement: Stevens (1946)Nominal scale, ordinal scale, interval scale, ratio scale
5 Selecting Scaling Method Nominal scale: allows for categorizingOrdinal scale: allows for rankingInterval scale: uses equal intervalsRatio scale: possesses real zero point
6 Representative scaling methods Expert rankingsMethod of equal-appearing intervalsLikert scalesMethod of empirical keyingRational scale construction (internal consistency)
7 Constructing the Items Should item content be homogeneous or varied?What range of difficulty should the items cover?How many initial items should be constructed?Which cognitive processes and item domains should be tapped?What kind of test item should be used?
8 Testing the ItemsIn conducting a thorough item analysis, the test developer might make use of item-difficulty index, item-reliability index, item-validity index, item-characteristic curve, and an index of item discrimination.
9 Item-difficulty index Generally, item difficulties that hover around 0.5, ranging between 0.3 and 0.7, maximize the information the test provides about differences between examinees.However, this rule of thumb is subject to one important qualification and one very significant exception.
10 Item-reliability index The product of point-biserial correlation and dispersion (standard deviation) of a item is the item-reliability index.
11 item-validity indexThe point-biserial correlation between the item score and the score on the criterion variable is computed first.Thus, the item-validity index consists of the product of the standard deviation and the point-biserial correlation.