Lecture+7

Overview

• Course Title: POSC 201: Political Research Design

• Instructor: Lewis Luartz

• Institution: Chapman University

• Lecture: Lecture 7

• Semester: Spring 2025

• Topics Covered:

  • Experimental and Non-experimental Designs (continued)

  • R Basics: Manipulating Data and Bivariate Correlations

Announcements and Reminders

• Homework Deadlines:

  • Homework 2: Due tonight by 11:59 PM (PST)

  • Homework 3: Assigned at end of class, due on Tuesday, March 11, 2025

• Midterm Exam: Scheduled for Thursday, March 20, 2025 (in-class)

• R Lessons:

  • Short R lessons will be integrated at the end of most classes; students should bring a computer

Experiments and Non-experimental Designs

The Classical Randomized Experiment

• Initial Steps:

  • Begins with sampling; availability sampling often used in lab settings due to participant access challenges

• Stimulus:

  • Essential test factor applied to participants for measuring effects

  • Central to hypotheses affecting the dependent variable and answering the research question

Group Assignment

• Types of Groups:

  • Experimental Group: Receives the treatment (independent variable)

  • Control Group: Does not receive any treatment

  • Essential to have one experimental group for each treatment applied

Randomization and Measurement

• Randomization:

  • Assigning groups randomly to ensure identical conditions between experimental and control groups

• Pretest Administration:

  • Measures responses before treatment; crucial for establishing initial benchmarks

  • Lack of a benchmark hinders evaluating treatment impact

Testing and Experimental Effects

• Posttest:

  • Measures responses after treatment to assess effects

  • Preexperimental and postexperimental measures help determine if treatment had an effect

• Experimental Effect:

  • Indicates response differences from treatment exposure

  • Should show variance in pretest and posttest results in the experimental group, while control group results should remain stable

R Time!

• Activity:

  • Students to open file "3 - R Data Basics - Manipulating Data and Bivariate Correlations.R" for practical application