Chapter 13: Scaling

Likert Scale

A Likert scale consists of a series of statements, each followed by a series of response alternatives. The numbers associated with each response are totaled to provide the overall score . The Likert is a summated rating scale. *Note: mid and neutral point Pros and Cons: -Offers range of choices -Provides at least ordinal level measurement -Straightforward construction -Summary score loses information

What is a Scale?

A scale is a number of items that combine to form a composite score on a variable. May involve multiple dimensions of a variable May involve degree to which a variable is present

Thurstone Scale

Constructed with equal-appearing intervals—assumes that the distance between any two adjacent points on the scale is the same. Items range from 1 (most unfavorable) to 11, (most favorable). Respondents select the item(s) with which they most agree.

Scaling of the Human Services

Example of linkage between research and practice. Strengthen intake process Aid to assessment for intervention planning Document progress of intervention Overall agency quality assurance monitoring system

Developing Scales I

First seek out existing scales Scale development principles: Obtain or develop a pool of possible items. Eliminate redundant, ambiguous or inappropriate items Pretest for validity and reliability Screen out items based on pretest Repeat process to select number of items desired.

Advantages of Scaling

Improved Validity Improved Reliability Increased Level of Measurement Increased Efficiency in Data Handling

Guttman Scale

In a Guttman scale, items have an inherently progressive nature relating to the intensity of the variable being measured. There is only one pattern of responses that will yield any given score on the scale. Reproducibility: the ability of each individual's composite score to predict exactly the items agreed and disagreed with. *Note: What is the breaking point of the idea/question/concern?

Response Bias

Response bias is the tendency for people's answers to questions to be influenced by things other than their true feelings, beliefs, and behaviors. Sources of response bias: -response set -response pattern anxiety -social desirability effect

Developing Scales II

Sources of Scale Items Researcher's imagination Judges—individuals knowledgeable about the topic Target population of the research Characteristics of Scale Items Validity Range of variation Unidimensionality—all items measure one variable

Semantic Differential Scales

The semantic differential format presents the respondent with a stimulus, such as a person or event, that is to be rated on a scale between a series of polar opposite adjectives. Pros and Cons: -Requires only four to eight adjective pairs per dimension for reliability of .80 or better. -Easy and less time consuming to construct. -Adjective pairs can be adapted from prior studies -Identifying the abstract dimensions is somewhat subjective and judgmental.

Thurstone vs. Likert

Thurstone -Interval level data -Quick response by users Likert -Possibly interval -Higher reliability with fewer items -Ease of construction