Indices and Scales To construct composite measures of variables, we need indices and scales Social science studies deal with many composite measures Many times, social researchers devise many questionnaire items to capture a single social concepts such as religiosity, alienation, etc Indices and scales are efficient data reduction techniques

Indexes versus Scales Indices and scales are ordinal measure of variables. A person’s score on either a score or an index gives an indication of his her relative religiosity Indexes and scales are composite measures of variables, measurements based on more than one data item. A person’s IQ is based on answers to a large number of test questions

Indexes and Scales are Different To construct an index of political activism, we ask respondents to answer the following questions and code them as yes = 1; no = 0 Do you write a letter to a public official? Do you sign a political petition? Do you give money to a political cause? Do you give money to a political candidate? Do you write a political letter to the editor? Do you persuade someone to change her or his voting plans?

Scales To measure political activism, we ask respondents to report Do you vote (yes=1, no =0)? Do you contribute money to a political campaign (yes = 2; no = 0)? Do you work on a political campaign (yes = 3, no =0)? Do you ran for office (yes = 4; no = 0)? However researchers often use indices rather than scales for the variable constructions

Index Construction Index construction includes the following steps Selecting items Examining empirical relations Scoring the index, and Validating the index

Item Selection 1) Face validity To measure religiosity, you ask respondents how much she believes in bible, how often she goes to church, and how often she prays 2) Unidimensionality A composite measure should represent only one dimension of a concept. Items measuring job satisfaction should not be included in a measure of organizational commitment

Item Selection 2 3) General or specific Religious commitment has three dimensions, each has a different set of indicators: commitment to pastors, commitment to church, and commitment to belief. 4) variance You need to distinguish people in your variable construction. What is the problem if you measure people’s tolerance of nuclear technique by asking “do you favor construction of a nuclear station very close to your backyard?”

Examination of Empirical Relationships Examining the empirical relationships among the items in the construction is the second step Bivariate relationship is a relationship between two variables Two indicators to measure U.S. participation in the United Nations. “Do you feel the U.S. financial support of the UN us (1), too high; (2) about right; or (3) too low? Should the United States contribute military personnel to UN peacekeeping actions (1) strongly approve; (2) mostly approve; (3) mostly disapprove; and (4) strongly disapprove

Three Org Commitment Questions The GSS 1991asked three org commitment questions (strong agree =1; agree = 2; disagree = 3; strongly disagree = 4) 1) I am proud to be working for this organization I would take almost any job to keep working for this organization I would turn down another job for more pay in order to stay with this organization

Bivariate Correlation

Multivariate Relationships Multivariate relationships involve more than two questionnaire items

Index Scoring Index scoring is to assign score to different items. In design of index items, you need to deal with two conflicting goals, a broad range of measurement, and an adequate number of cases in each responses To measure people’s tolerance of nuclear technology, you have a very broad range items from “Constructing nuclear power station close to your backyard” to “absolutely no nuclear based station should be constructed anywhere in the world”

Index Scoring 2 Unless you can justify use of different weight, each item carries the same weight The 1996 GSS asked respondents to report 1) Last time, I felt angry that involved workplace 2) Last time I felt angry involving family members 3) Last time, I felt angry involving government Yes = 1; no =0 applies to every question

Handling Missing Data Reasonable guess: a person filled in every “yes” box and left every “no” box blank A person answering “do not know” to “Jehovah witness religion” is actually a “disbeliever” Assigning mean/median to every missing cases, will may produce biased estimates in regression coefficients

Index Validation Validating an index means to measure whether that index capture what it intends to measure. For example, whether the index for political conservatism really measure people’s political view towards conservatism. The following are several ways of measuring index validity

Item Analysis Item analysis/internal validation examines the extent to which the index is related to the individual items it comprises. Index of organizational commitment

Index of Org Commitment Index

External Validation Those score high on one org commitment item should score high on the other two org commitment items too. An external validation indicates the degree to which such a consistency accomplishes.

Bad Index and Bad Validators When an index fails to pass the validation test, it could be either 1) the index does not adequately measure the variables in questions, or 2) the validation items do not adequately measure the variable and do not provide a sufficient test of the index