3/29/2012. Chapter 7 Measurement of Variables: Scales, Reliability and Validity. Scales. Scale

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1 Chapter 7 Measurement of Variables: Scales, Reliability and Validity Scales A scale is a mechanism or tool by which unit of analysis are distinguished on the variables of the interest of the study. Every scale should have at least two important qualities Exhaustiveness You should be able to classify every observation (or response) in terms of the attributes composing the variable (scale). Assist. Prof. Dr. Özge Özgen Research Methodology Mutually Exclusiveness You should be able to classify every observation (or response) in terms of one and only one attribute composing the variable (scale). Examples (exhaustiveness and mutually exclusiveness) Q: What is your education level? Not Exhaustive Exhaustive 1) Elementary school 1) No education 2) Junior high school 2) Elementary school 3) High school 3) Junior high school 4) University 4) High school 5) University 6) Above university Q: What is your work schedule? Not Mutually Exclusive Mutually Exclusive 1) Full-time 1) Full-time 2) Part-time 2) Part-time 3) Both Indicators for Dimension 2 (Figure 8.1) 1. How often do they think of work while at home. 2. Whether they have any hobbies. 3. How they spend their time off the job. Some Possible Questions for each indicator (Figure 8.1) 1. How frequently do you think of work while at home? (1) Often (2) Sometimes (3) Never 2. Do you have any hobbies? If so, how many hours do you spend a week for your hobbies? (1) More than 4 (2) 4 to 2 (3) Less than 2 3. How frequently do you engage in the following activities? Please answer using the following scale: (1: Often, 2: Sometimes, 3: Never) A. Going to movies, theatre, concerts B. Spending your weekend with your family C. Coming together with friends Assigning a scale for each question. Scale A set of symbols or numbers so constructed that the symbols or numbers can be assigned by rule to the individuals to whom the scale is applied. Series of items arranged according to value or magnitude for the purpose of quantification Series of items are assigned by rule A continuous spectrum NOMINAL ORDINAL INTERVAL RATIO Copyright 2003 John Wiley & Sons, Inc. Sekaran/RESEARCH 4E 8F 1

2 At which market do you shop most frequently? Kipa Metro Migros Tansaş Pehlivanoğlu Other 8B Rank the following five characteristics in a job in terms of how important they are for you. You should rank the most important item as 1, the next in importance as 2, and so on. Job Characteristics Ranking the importance Interact with others... Use a number of different skills... Complete a whole task from beginning to end... Work independently... 8C Indicate the extent to which you agree with the following statements as they relate to your job by using following scale Strongly Disagree Disagree Neither Agree Nor Disagree Agree Working independetly is very important for me Using different skills at job is very important for me Strongly Agree D What is your monthly household income?... 8E Refreshments!... Exercises 8G 2

3 The Measuring Process Ranking - Rank order preference Rating - Estimates magnitude of a characteristic Sorting - Arrange or classify concepts Choice - Selection of preferred alternative Ranking tasks require that the respondent rank order a small number of objects in overall performance on the basis of some characteristic or stimulus. Sorting might present the respondent with several concepts typed on cards and require that the respondent arrange the cards into a number of piles or otherwise classify the concepts. Rating asks the respondent to estimate the magnitude of a characteristic, or quality, that an object possesses. The respondent s position on a scale(s) is where he or she would rate an object. Simple Attitude Scaling Choice between two or more alternatives is another type of attitude measurement - it is assumed that the chosen object is preferred over the other. In its most basic form, attitude scaling requires that an individual agree with a statement or respond to a single question. This type of self-rating scale merely classifies respondents into one of two categories; THE PRESIDENT SHOULD RUN FOR RE-ELECTION AGREE DISAGREE 3

4 Category Scales Example of Category Scale A category scale is a more sensitive measure than a scale having only two response categories - it provides more information. Questions working is an extremely important factor in the usefulness of these scales. How important were the following in your decision to visit San Diego (check one for each item) VERY SOMEWHAT NOT TOO IMPORTANT IMPORTANT IMPORTANT CLIMATE COST OF TRAVEL FAMILY ORIENTED EDUCATIONAL/ HISTORICAL ASPECTS FAMILIARITY WITH AREA The Likert Scale Likert Scale for Measuring Attitudes Toward Tennis An extremely popular scale for measuring attitudes. Respondents indicate their own attitudes by checking how strongly they agree or disagree with statements. Response alternatives: strongly agree, agree, uncertain, disagree, and strongly disagree. Playing tennis is the best way to exercise. Strongly Agree Agree Not Sure Disagree Strongly Disagree Semantic Differential A series of seven-point bipolar rating scales. Bipolar adjectives, such as good and bad, anchor both ends (or poles) of the scale. Semantic Differential Scales for Measuring Attitudes Toward Tennis Exciting : : : : : : : Calm Interesting : : : : : : : Dull Simple : : : : : : Complex Passive : : : : : : Active 4

5 Numerical Scales Stapel Scales Numerical scales have numbers as response options, rather than semantic space or verbal descriptions, to identify categories (response positions). Modern versions of the Stapel scale place a single adjective as a substitute for the semantic differential when it is difficult to create pairs of bipolar adjectives. The advantage and disadvantages of a Stapel scale, as well as the results, are very similar to those for a semantic differential. However, the Stapel scale tends to be easier to conduct and administer. A Stapel Scale for Measuring a Store s Image Behavioral Differential Scale Wide Selection Department Store Name The behavioral differential instrument has been developed for measuring the behavioral intentions of subjects towards any object or category of objects. A description of the object to be judged is placed on the top of a sheet, and the subjects indicate their behavioral intentions toward this object on a series of scales. For example: A 25-year old woman sales representative Would : : : : : : : Would Not Ask this person for advice. Fixed or Constant Sum Scale Divide 100 points among each of the following brands according to your preference for the brand: Graphic Rating Scales A graphic rating scale presents respondents with a graphic continuum. Brand A Brand B Brand C Good Poor 5

6 Graphic Rating Scale Stressing Pictorial Visual Communications Example Design a Likert type, semantic differential type, staple type scale in order to measure service quality level of Faculty canteen Good Poor Reliability and Validity on Target Low Reliability High Reliability Reliable but Not Valid (Target A) (Target B) (Target C) 6