Your Decision-Making Toolkit: Part 2
Unit 1 · Lesson 1.4 · Last updated September 18, 2026
A 45-minute lesson introducing the marginal and interdependence principles of economic thinking, with practice applying all four principles to real-world decision making.
Overview
In this lesson, students learn about the two remaining principles of economic thinking, the marginal and interdependence principles, and have a chance to practice applying the principles of economic thinking to decision making. Explicit connections are made between these principles and the primary activity in Lesson 1.2. This lesson assumes that students were introduced to the first two principles of economic thinking in Lesson 1.3.
Learning Objectives
- Describe the marginal principle and explain the role it plays in decision making.
- Describe the interdependence principle and explain the role it plays in decision making.
Materials
- Instruction Slides (display during class period)
- Activator Messages (1 copy per student)
- Student Handout (previously distributed)
- Retrieval Practice (1 copy per student)
- Optional: Text Message Template (to customize the Activator Messages)
Lesson Sequence
Slides 2–5
- Display Slide 2. Distribute 1 copy of the Activator Messages to each student. Allow students 3 minutes to individually follow the instructions on the slide. After 3 minutes, tell students to share their responses to the prompt with a peer, then call on two students to share with the class. Note: this activity is designed to let students practice for the Unit 1 summative assessment. Additional educator tips, details, and suggested answers are in the notes section throughout the Instruction Slides.
- Advance to Slide 3. Click to reveal the text on the slide and elaborate on the student responses as needed.
- Proceed to Slide 4. Tell students to retrieve the Student Handout distributed in Lesson 1.3.
- Display Slide 5 and introduce the learning objectives for the lesson.
Slides 6–19
- Proceed through Slides 6 and 7 to remind students that, in the previous lesson, they learned about the first two principles of economic thinking and how to use those principles as a framework for decision making.
- Advance to Slide 8 and click to reveal the text introducing the marginal principle. Note: you may want to alert students to the anchor question on Slide 8, "One more?", as a helpful tool for applying the marginal principle. Remind students throughout the lesson that they may add notes to the Student Handout.
- Display Slide 9. Ask students to recall their choices from the primary activity in Lesson 1.2 and answer the questions on the slide with a peer. Click to explain that students were applying the marginal principle in their decision making.
- Proceed to Slide 10. Click to guide students through the decision-making graphic to illustrate how the marginal principle and cost-benefit principle are applied.
- Progress through Slides 11–12. Explain how thinking at the margin supports the maximization of benefits, and define rational behavior.
- Proceed to Slide 13. Direct students to discuss their answers with a peer to assess their ability to identify choices that require marginal decision making.
- Progress to Slide 14 to reveal the correct responses and explain as needed.
- Display Slide 15. Use the text on the slide to emphasize that not all decisions involve the marginal principle.
- Progress through Slides 16–17 to transition to the interdependence principle. Click to reveal the text on Slide 17 to introduce the interdependence principle. Note: you may want to alert students to the anchor question on Slide 17, "What else?", as a helpful tool for applying the interdependence principle.
- Use Slides 18–19 to illustrate examples of applying the interdependence principle from the primary activity in Lesson 1.2 and from students' lives. Pause between slides to allow students to discuss their answers with a peer, then debrief the questions as a class.
Slides 20–30
- Advance to Slide 20. Tell students that they will now explain how the principles of economic thinking apply to decisions.
- Use Slides 21–25 to guide students through the process of identifying and explaining how the principles of economic thinking apply to a scenario.
- Proceed to Slide 26. Remind students to consult the anchor questions on the Student Handout as they collaborate with a peer to identify and explain how the principles apply to the personal finance scenario on the slide. Allow approximately 3 minutes for pairs to analyze and discuss the scenario, then conduct a class discussion to debrief. Use Slide 27 as needed.
- Advance to Slide 28 and repeat the previous step with the new scenario. Use Slide 29 to debrief as needed.
- Display Slide 30. Use the text on the slide to emphasize that not all decisions involve the marginal principle.
Slides 31–32
- Progress through Slides 31–32. Tell students that for this portion of the class they will work alone. Distribute 1 copy of Retrieval Practice to each student and explain that it is a low-stakes opportunity to assess their current level of understanding.
- Allow students 10 minutes to complete Retrieval Practice, including the portion that calls for the Reinforcement Readings, using the instructions on the handout. Note: students are given all sections of the Reinforcement Readings so they have additional examples of each principle of economic thinking.
- Collect Retrieval Practice and review it for common misconceptions or gaps in understanding to address at the start of the following class.
Aligned Standards
Voluntary National Content Standards in Economics
Standard 1 Scarcity and Allocation
Standard 2 Decision-Making
What Educators Are Saying
The lessons were easy to implement and my students enjoy them.
High School Economics Teacher, Virginia
Students respond to Econiful because the lessons feel relevant, interactive, and connected to the world they are actually living in.
High School Economics Teacher, Illinois
The curriculum is all organized and it is extremely easy to understand and use.
High School Economics Teacher, Washington