Causal-Comparative Research: Design, Threats, and Survey Methods, Study notes of Design Patterns

Download Causal-Comparative Research: Design, Threats, and Survey Methods and more Study notes Design Patterns in PDF only on Docsity! 1 Causal-Comparative Designs Steps Involved in Causal- Comparative Research • Problem Formulation • The first step is to identify and define the particular phenomena of interest and consider possible causes • Sample • Selection of the sample of individuals to be studied by carefully identifying the characteristics of select groups • Instrumentation • There are no limits on the types of instruments that are used in Causal-comparative studies • Design • The basic design involves selecting two or more groups that differ on a particular variable of interest and comparing them on another variable(s) without manipulation (see Figure 16.1) The Basic Causal-Comparative Designs Independent Dependent Group variable variable (a) I C O (Group possesses (Measurement) characteristic) II –C O (Group does (Measurement) not possess characteristic) (b) I C1 O (Group possesses (Measurement) characteristic 1) II C2 O (Group possesses (Measurement) characteristic 2) Examples of the Basic Causal- Comparative Design Threats to Internal Validity in Causal-Comparative Research • Subject Characteristics • The possibility exists that the groups are not equivalent on one or more important variables • One way to control for an extraneous variable is to match subjects from the comparison groups on that variable • Creating or finding homogeneous subgroups would be another way to control for an extraneous variable • The third way to control for an extraneous variable is to use the technique of statistical matching 2 Does a Threat to Internal Validity Exist? (Figure 16.3) Other Threats • Loss of subjects • Location • Instrumentation • History • Maturation • Data collector bias • Instrument decay • Attitude • Regression • Pre-test/treatment interaction effect Evaluating Threats to Internal Validity in Causal-Comparative Studies • Involves three sets of steps as shown below: – Step 1: What specific factors are known to affect the variable on which groups are being compared or may be logically be expected to affect this variable? – Step 2: What is the likelihood of the comparison groups differing on each of these factors? – Step 3: Evaluate the threats on the basis of how likely they are to have an effect and plan to control for them. Data Analysis • In a Causal-Comparative Study, the first step is to construct frequency polygons. • Means and SD are usually calculated if the variables involved are quantitative. • The most commonly used inference test is a t-test for differences between means. • Results should always be interpreted with caution since they do not provide strong evidence of cause and effect. • It is common to find researchers who treat quantitative variables conceptually as if they were categorical, but nothing is gained by this procedure and it should be avoided. Survey Research Chapter Seventeen What is a Survey? • Researchers are often interested in the opinions of a large group of people about a particular topic or issue. • There are three major characteristics that most surveys possess: 1) Information is collected from a group of people in order to describe some aspect of the population 2) Information is collected by asking questions of the members of the selected group 3) Information is collected from a sample rather than from every member of the population