Refined Shampoo Dose-Response Experiment for Bean Plants

Building on the previous design, this version uses a geometric concentration series for clearer dose-response resolution:

Experimental Design

Protocol

• Use same shampoo brand/batch for all treatments.
• Prepare fresh solutions weekly; apply equal volumes per pot.
• Plant 4 bean seeds per pot, ¼ inch deep.
• Thin to 2 uniform seedlings per pot at 7 days.
• Measure height, leaf count, chlorophyll (SPAD meter if available) weekly.

Analysis

Plot growth metrics vs. log(shampoo concentration). Calculate EC₅₀ (effective concentration for 50% growth reduction). This demonstrates quantitative toxicology principles appropriate for middle school.