A science fair judge analyzes data from 3 student experiments testing plant growth with different fertilizers. Group A (fertilizer X) had average growth 18.5 cm (n=12), Group B (Y) 21.2 cm (n=15), Group C (Z) 19.8 cm (n=13). What is the overall average growth across all plants? - Decision Point

Understanding the Context

Why Are Student Fertilizer Experiments Gaining Attention Now?

Plant-based inquiry has surged in recent years as part of a broader U.S. push toward STEM education, eco-conscious living, and data literacy. Young scientists are increasingly testing variables like soil nutrients and organic versus synthetic inputs, mirroring real-world farming research. Social media and school projects now spotlight these growing experiments, amplifying public interest in how simple changes affect growth. The collaborative, curious nature of these assessments invites others to explore similar questions—transforming neighborhood gardens and classrooms into living laboratories. As climate awareness deepens, understanding optimal plant nourishment also becomes a practical concern, linking plant science to broader environmental stewardship.

Key Insights

Calculating the True Average: How Growth Data Adds Up

To determine the overall average growth across all three fertilizer groups, a straightforward statistical average connects the individual group means weighted by their sample sizes. This method ensures larger groups—like Group B—carry more influence in the final result.

Group A (X): 18.5 cm × 12 plants = 222 cm total growth
Group B (Y): 21.2 cm × 15 plants = 318 cm total growth
Group C (Z): 19.8 cm × 13 plants = 257.4 cm total growth

Combined total growth: 222 + 318 + 257.4 = 797.4 cm
Total number of plants: 12 + 15 + 13 = 40

Average growth across all plants: 797.4 ÷ 40 = 19.935 cm

Final Thoughts

Rounded to one decimal place, the overall average is 19.9 cm—indicating a balanced baseline across these student experiments. This blended