Unit 3 - Lesson 7 Unit Review
Review and Application of Data Collection
Unit 3, Topics 3.1–3.9: Review and Application of Data Collection
Overview
This lesson reviews the full range of data collection concepts, from observational studies (watching natural patterns without intervention) versus experiments (manipulating factors to test causation), to sampling methods (like SRS or stratified for fair representation) and biases (such as undercoverage or nonresponse that skew results), culminating in experimental design principles like blocking and randomization to control confounders. Mastering these ensures studies produce trustworthy data, bridging planning to execution.
Example: Reviewing a smoking survey (observational, suggesting lung links) vs. a nicotine patch trial (experiment, claiming causation via random assignment).
Sampling methods and biases are revisited to highlight how poor choices limit reliability, while experimental design tools like control and blinding strengthen validity against hidden influences. The goal is to apply these holistically for better study outcomes.
Example: Stratified sampling by age in a voter poll avoids youth undercoverage bias, unlike voluntary online responses that overrepresent enthusiasts.
The unit ties together by emphasizing how designs affect claims' strength, with practice reinforcing justification and ethical awareness for real-world use.
Example: In a diet app test, random replication and consent review generalizes findings ethically, unlike biased self-reports.
Assignment:
Part 1: Guided Practice Activity
Consider the example of reviewing a flawed school wellness program evaluation, where surveys (observational) on exercise habits were voluntary, and an experiment on app use lacked randomization. Follow the tasks below to review concepts and apply them.
Example Scenario: 200 students surveyed on activity levels, then 50 tested an app without blocks for fitness differences.
Tasks:
- Reviewing Key Concepts:
- Summarize observational studies vs. experiments, sampling methods, bias, and experimental design, with one key difference or tool for each.
Example: Observational watches habits (associations only) vs. experiments manipulate (causation via control); sampling like SRS ensures randomness; bias such as nonresponse skews replies; design uses blocking to handle confounders like age. - Extra Practice: For a community garden yield study, summarize two concepts each from observational/experimental and sampling/bias.
- Summarize observational studies vs. experiments, sampling methods, bias, and experimental design, with one key difference or tool for each.
- Practicing AP-Style Questions:
- Apply to 2019 FRQ 6 (experimental design for plant growth): Describe method, justify randomization, and note bias risks.
Example: Random assign seeds to light treatments with control soil; randomization balances growth factors; risks nonresponse if plants die early, addressed by replication. - Write 1-2 sentences justifying choices for the wellness scenario (e.g., "Add stratified sampling to fix voluntary bias.").
- Apply to 2019 FRQ 6 (experimental design for plant growth): Describe method, justify randomization, and note bias risks.
- Gallery Walk Simulation (Individual):
- Display your study design (sketch or describe) and critique for bias/control (e.g., "My app test lacks blinding, risking placebo; add double blind.").
Example: Design: Random 25 to app/25 control for activity; critique: Good randomization reduces selection bias, but no replication—add weekly checks for validity. - Write 2-3 sentences on peer-like feedback for the wellness program.
Example: "Voluntary surveys show control weakness; improve with random assignment to app groups and blinding to cut response bias, enhancing claims on program impact."
- Display your study design (sketch or describe) and critique for bias/control (e.g., "My app test lacks blinding, risking placebo; add double blind.").
Part 2: Independent Practice
Review Unit 3 by redesigning a biased coffee vs. tea alertness study (50 office workers, voluntary sign-up, no randomization, self-reported focus).
Tasks:
- Summarize key concepts applied.
- Practice an AP-style question: Justify a redesigned method for the study, including randomization and control.
- Simulate a Gallery Walk critique: Describe your design and note 2 strengths/weaknesses for bias/control.
- Write 2-3 sentences interpreting redesigned results with limitations.
- Extra Activity: Invent a Unit 3 review scenario. Summarize concepts, justify design, and critique.