Question

Ali hypothesized that increasing fertilizer would increase plant growth. Four groups of thirty similar plants were given 0 to 15 ml of fertilizer, as shown in the graph. The change in plant height for each group over a two-week period was averaged and recorded.

Plant Group
Fertilizer Added (mL)
Avg. Growth (cm)
A
0
4
B
5
6
C
10
8
D
15
3

What is the best conclusion based on this data?
The hypothesis was not supported because the data indicated that fertilizing plants does not improve plant growth.
The hypothesis was supported; to get the best growth, use 5 milliliters of fertilizer per plant.
The hypothesis was not supported; the data indicated that too much fertilizer can inhibit plant growth.
The hypothesis was supported; to get the best growth, use 15 milliliters of fertilizer per plant.

Answer 1

The hypothesis was not supported; the data indicated that too much fertilizer can inhibit plant growth.

Reason: growth increased from 0 → 10 mL (4 → 8 cm) but fell at 15 mL (3 cm), so increasing fertilizer does not always increase growth.