Evidence-Based Scientific Inquiry Theories and Hypotheses

Science the “use of evidence to construct testable explanations and predictions of natural phenomena as well as the knowledge generated through this process” Science has limitations: some questions are outside the realm of science because they deal with phenomena that are not scientifically testable. Scientific inquiry may be limited by current technology

Hypothesis Widely tested can have durable explanatory power may be incorporated into theories

Theory a well-established and highly reliable explanation that may be subject to change as new areas of science and new technologies are developed Scientific theories: Are based on natural and physical phenomena Are capable of being tested by multiple independent researchers Are well-established and highly reliable explanations May be subject to change as new areas of science and new technologies are developed when new evidence is inconsistent with or cannot be explained by current theory

Variable A variable is something that can be changed, such as a characteristic or value.

Independent Variable the variable that is changed or controlled in a scientific experiment The independent variable is deemed independent because the experimenters are free to vary it as they need. Independent variables are the variables that the experimenter changes to test their dependent variable. The effect on the dependent variable is measured and recorded. Independent Variable Example: A scientist is testing the effect of light and dark on the behavior of moths by turning a light on and off. The independent variable is the amount of light. A change in the independent variable directly causes a change in the dependent variable.

Dependent Variable the variable that is being measured in an experiment The dependent variable is dubbed dependent because it is thought to depend in some way on the variations of the independent variable. Dependent Variable Example: A scientist is testing the effect of light and dark on the behavior of moths by turning a light on and off. The dependent variable is the moth's reaction to the light.

Examples of Independent/Dependent Variables Researchers want to discover if listening to classical music helps students earn better grades on a math exam. Researchers are interested in seeing how long it takes people to respond to different sounds. Researchers want to know whether first-born children learn to speak at a younger age than second-born children. Researchers are interested in looking at how alcohol use influences reaction times while driving.

Answers In the 1st example, the classical music is the independent variable and the scores on the math exams are the dependent variable. In the 2nd example, the independent variable is the different sounds, the length of time it takes participants to respond to a sound is the dependent variable. In the 3rd example, learning to speak is the independent variable, the dependent variable is the age at which the child learns to speak. In the 4th example, the amount of alcohol a participant injects is the independent variable, while their performance on a driving test is the dependent variable.

Control A control variable is any factor you control or hold constant during an experiment. A control variable is also called a controlled variable or constant variable. Example: If you are studying the effect of the amount of water on seed germination, control variables might include temperature, light, and type of seed. A control group is a set of experimental samples or subjects that are kept separate and aren't exposed to the independent variable. Example: In an experiment to determine whether zinc helps people recover faster from a cold, the experimental group would be people taking zinc, while the control group would be people taking a placebo (not exposed to extra zinc, the independent variable).

Problem - A question to be considered, solved or answered Observation - An observation is the act of noting and recording something with instruments. Hypothesis - A hypothesis is a tentative explanation that accounts for a set of facts and can be tested by further investigation. Experiment - An experiment is a test under controlled conditions that is made to demonstrate a known truth, or examine the validity of a hypothesis. Data is collected (data is the information collected during an experiment). Conclusion - A conclusion is the result or outcome of an act or process. Theory - An assumption based on limited information or knowledge. POHEC - The mnemonic device used to help you remember the steps of the scientific method.