Variables, Hypothesis, and Graphs
This review material covers key scientific method concepts including defining independent, dependent, and controlled variables, identifying variables across scenario examples, formulating structured 'If..., then..., because...' hypotheses, and evaluating bar graphs.
1. Core Variable Definitions and Practice
Independent Variable (IV)
The factor that you change in an experiment, representing the variable you are curious about.
Dependent Variable (DV)
The factor you measure to collect experimental data.
Constants / Controlled Variables
The factors that remain unchanged throughout the entire experiment.
Scenario Description | Independent Variable | Dependent Variable | Constants |
Effect of fuel types on engine performance in a car | Fuel Type | Engine performance | car, driver, driving, location and speed |
Health effects of second-hand smoke on hamsters | amount of second-hand smoke | health | food, age, environment |
Effect of climbing high altitudes on climber memory | the altitude of the climb | The climbers memory | climbers health, climbing environment |
Math test performance across different student ages | age of tester | number of correct answers | how much sleep they got, what they ate, the math test |
Lobster claw growth from drinking Pepsi-contaminated water | amount of contaminated water drunk | claw size | formula of water, age of lobster, claw size before |
2. Experimental Design and Hypothesis Construction
Problem Identification
Erika observed that her baked birthday cake had not risen after being taken out of the oven.
Hypothesis Formulation
She hypothesized: 'If the oven doesn't heat to the correct temperature, then the cake will not rise.'
Experimental Result & Conclusion
An internal oven thermometer measured 375 ºF, demonstrating the oven heated properly and refuting her hypothesis.
Alka-Seltzer Temperature: If the water temperature rises, then the tablet will dissolve faster, because warm water dissolves things faster.
Alka-Seltzer Soda Addition: If you add soda to the water, then the tablet will dissolve faster, because the bubbles dissolve the tablet well.
Plant Growth & Light: If a plant has more light, then it will grow faster, because light speeds up plant growth.
Plant Growth & Water: If a plant gets more water, then it will grow faster, because water helps plants grow.
3. Graph Interpretation and Data Evaluation
Insects Collected by Trap Type
Trap C collected the highest count of Honeybees, while Trap B collected the most Hornets.
Independent Variable: The type of insect trap (Trap A, Trap B, Trap C).
Dependent Variable: How many insects were collected.
Graph Improvement: The graph is missing a labeled y-axis to indicate numerical values.
Optimal Honeybee Trap: Trap C was the most effective trap for collecting Honeybees.