a method for learning about reality through systematic observation and experimentataion
the practice of basing conclusions on facts without influence of personal emotion and bias
the ability to think clearly, rationally, and independently
a set of facts and relationships between facts that can explain and predict related phenomena
a proposed explanation for a situation
the process of having other experts review ones research before it's published
repeating an experiment and getting the same results
research methods designed for making careful, systematic observations
an in-depth analysis of the behavior of one person or a small group
an in-depth study of a phenomenon in its natural setting
a descriptive in which participants are asked the same questions
a subset of a population being studied
the entire group from which a sample is taken
a measure of the direction and strength of relationship between two variables
a factor that has a range of values
a method for describing a variables quantity
a variable that is responsible for a correlation observed between two other variables of interest
a research method that tests hypotheses and allows researchers to make conclusions about causality
an experimental variable controlled and manipulated by the experimenter
a measure that demonstrates the effects of an independent variable
a group that experiences all experimental procedures with the exception of exposure to the independent variable
a group of participants that is exposed to the independent variable
the procedure in which each participant has an equal chance of being assigned to any group in an experiment
variables that are irrelevant to the hypothesis being tested but can alter a researcher's conclusions
defining variables in practical terms
a statistical analysis of many previous experiment on a single topic
both the participants and the researchers don't know whether the participant was given the real treatment of the placebo
fake treatment that can't be distinguished from a real treatment
an experimental design for for assessing age-related changes in which data are obtained simultaneously from people of differing ages
an experimental design for assessing age-related changes in which data are obtained from the same individuals at intervals over a long period of time
mixed longitudinal design
method for assessing age-related changes that combines the cross-sectional and longitudinal approaches by observing a cross-section of participants over a shorter period than is used in typical longitudinal studies
a quality of a measure that leads to valid conclusions
statistical methods that organize data into meaningful patterns and summaries
numerical average set of scores
halfway mark in a set of data
the most frequently occurring score in a set of data
a measure of how tightly clustered a group of scores is around the mean
a symmetrical probability function
statistical methods that allow experimenters to extend conclusions from samples the larger populations
to extend conclusions to larger populations outside your research sample
a hypothesis stating the default position that there is no real difference between two measures
a standard for deciding whether and observed result is because of chance
permission obtained from a research participant after risks and benefits of an experimental procedure have been thoroughly explained
Learning Objectives
Although many have taken science classes throughout the course of their studies, people often have incorrect or misleading ideas about some of the most important and basic principles in science. Most students have heard of hypotheses, theories, and laws, but what do these terms really mean? Prior to reading this section, consider what you have learned about these terms before. What do these terms mean to you? What do you read that contradicts or supports what you thought?
What is a Fact?
A fact is a basic statement established by experiment or observation. All facts are true under the specific conditions of the observation.
What is a Hypothesis?
One of the most common terms used in science classes is a "hypothesis". The word can have many different definitions, depending on the context in which it is being used:
- An educated guess: a scientific hypothesis provides a suggested solution based on evidence.
- Prediction: if you have ever carried out a science experiment, you probably made this type of hypothesis when you predicted the outcome of your experiment.
- Tentative or proposed explanation: hypotheses can be suggestions about why something is observed. In order for it to be scientific, however, a scientist must be able to test the explanation to see if it works and if it is able to correctly predict what will happen in a situation. For example, "if my hypothesis is correct, we should see ___ result when we perform ___ test."
A hypothesis is very tentative; it can be easily changed.
What is a Theory?
The United States National Academy of Sciences describes what a theory is as follows:
"Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena."
"A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter (stating that everything is made of atoms) or the germ theory of disease (which states that many diseases are caused by germs). Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.
Note some key features of theories that are important to understand from this description:
- Theories are explanations of natural phenomena. They aren't predictions (although we may use theories to make predictions). They are explanations as to why we observe something.
- Theories aren't likely to change. They have a large amount of support and are able to satisfactorily explain numerous observations. Theories can, indeed, be facts. Theories can change, but it is a long and difficult process. In order for a theory to change, there must be many observations or pieces of evidence that the theory cannot explain.
- Theories are not guesses. The phrase "just a theory" has no room in science. To be a scientific theory carries a lot of weight; it is not just one person's idea about something
Theories aren't likely to change.
What is a Law?
Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Usually scientific laws refer to rules for how nature will behave under certain conditions, frequently written as an equation. Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics. As a comparison, theories explain why we observe what we do and laws describe what happens.
For example, around the year 1800, Jacques Charles and other scientists were working with gases to, among other reasons, improve the design of the hot air balloon. These scientists found, after many, many tests, that certain patterns existed in the observations on gas behavior. If the temperature of the gas is increased, the volume of the gas increased. This is known as a natural law. A law is a relationship that exists between variables in a group of data. Laws describe the patterns we see in large amounts of data, but do not describe why the patterns exist.
What is a Belief?
A belief is a statement that is not scientifically provable. Beliefs may or may not be incorrect; they just are outside the realm of science to explore.
Laws vs. Theories
A common misconception is that scientific theories are rudimentary ideas that will eventually graduate into scientific laws when enough data and evidence has accumulated. A theory does not change into a scientific law with the accumulation of new or better evidence. Remember, theories are explanations and laws are patterns we see in large amounts of data, frequently written as an equation. A theory will always remain a theory; a law will always remain a law.
Video \(\PageIndex{1}\): What’s the difference between a scientific law and theory?
Summary
- A hypothesis is a tentative explanation that can be tested by further investigation.
- A theory is a well-supported explanation of observations.
- A scientific law is a statement that summarizes the relationship between variables.
- An experiment is a controlled method of testing a hypothesis.