Processes of Science

Designing an Experiment

Typically begins with observations that lead to a questionTests a hypothesis (prediction)Collect information under controlled conditions. Control group – all conditions kept normal Experimental group (test group) – all

conditions kept the same as the control except for the single condition being tested

Variables

Independent variable – condition that is changed: affects the outcome(a.k.a. the manipulated variable)

Dependent Variable – changes in this condition depend on changes in the independent variable(a.k.a. the responding variable)

Variables

Ex. You want to test the effect of calcium additives on the growth of tomato plants. What is the independent variable?

What is the dependent variable?

Your control group would be put in what conditions?

Amount of calcium

Growth of tomato plants

Normal soil without calcium added

Data

Quantitative – numerical counts or measurements Scientific measurements are always

metric! Reported in graphs or tables

Qualitative (descriptive) – written descriptions

When would you use each of these?Data often presented in tables or graphs.

Conclusions

Data lends support for or against the hypothesis When a hypothesis is supported over time by

many investigations is becomes a theory A theory is an explanation of a scientific

event. Ex. Theory of Inheritance

Facts of nature generally known to be true are laws Ex. Law of Gravity

What is the difference between a theory & a law?

A theory is an explanation of why something happens

A law simply describes a natural phenomenon (does not explain why).

Theories & laws are accepted to be equally legitimate.

Peer review

Results from experiments are reported to the scientific community.

Why is this important?

The researcher may then repeat the experiment to verify results, or redesign the experiment as needed.