Scientific Method and Evidence

Overview

This lecture explains the scientific method, how hypotheses are tested using controlled experiments, and the importance of evidence in science.

Science uses a structured approach called the scientific method.
The three core steps are: observation, forming a hypothesis, and experimentation.
A hypothesis is an explanation for an observation; it is often called an educated guess.
Hypotheses must be reasonable (fit with existing knowledge) and testable.
Explanations that cannot be tested experimentally are not considered scientific hypotheses.

Science relies on evidence gathered through observation and experimentation rather than assumptions.
An experiment is designed to test the hypothesis and produce results supporting or refuting it.
Controlled experiments isolate one variable while keeping all others constant to ensure valid results.
The results can lead to modifying the hypothesis and further experiments.
Science differs from philosophy because it requires experimental evidence, not just logical reasoning.

Hypothesis: Chemical X speeds the growth of corn.
Use two groups of plants (Group A with Chemical X, Group B without).
Assign plants randomly to each group to account for natural genetic variation.
Keep all other conditions (light, soil, water, etc.) identical for both groups.
Measure plant growth and compare results to see if Chemical X has an effect.
Significant differences in growth, measured and analyzed statistically, provide evidence for the hypothesis.

Scientific method — a systematic process for gaining knowledge through observation, hypothesis formation, and experimentation.
Hypothesis — a testable explanation for an observation, sometimes called an educated guess.
Controlled experiment — an experiment where only one variable changes and all other factors are held constant.
Evidence — data collected through experiments or observations used to support or disprove a hypothesis.
Variable — any factor or condition that can change in an experiment.