He could grow maple trees in a warm enclosed environment such as a greenhouse and see if their leaves still dropped in the fall. The hypothesis is also falsifiable. If the leaves still dropped in the warm environment, then clearly temperature was not the main factor in causing maple leaves to drop in autumn. In the Try It below, you can practice recognizing scientific hypotheses. As you consider each statement, try to think as a scientist would: can I test this hypothesis with observations or experiments?
Is the statement falsifiable? This statement is not testable or falsifiable. But some would question whether the people in that place were really wicked, and others would continue to predict that a natural disaster was bound to strike that place at some point. These researchers investigated whether a vaccine may reduce the incidence of the human papillomavirus HPV. Preliminary observations made by the researchers who conducted the HPV experiment are listed below:.
Researchers have developed a potential vaccine against HPV and want to test it. What is the first testable hypothesis that the researchers should study? The next step is to design an experiment that will test this hypothesis.
There are several important factors to consider when designing a scientific experiment. First, scientific experiments must have an experimental group. This is the group that receives the experimental treatment necessary to address the hypothesis. The experimental group receives the vaccine, but how can we know if the vaccine made a difference? Many things may change HPV infection rates in a group of people over time.
To clearly show that the vaccine was effective in helping the experimental group, we need to include in our study an otherwise similar control group that does not get the treatment. We can then compare the two groups and determine if the vaccine made a difference. The control group shows us what happens in the absence of the factor under study. A placebo is a procedure that has no expected therapeutic effect—such as giving a person a sugar pill or a shot containing only plain saline solution with no drug.
Moreover, if the doctor knows which group a patient is in, this can also influence the results of the experiment. Without saying so directly, the doctor may show—through body language or other subtle cues—his or her views about whether the patient is likely to get well.
Both placebo treatments and double-blind procedures are designed to prevent bias. Bias is any systematic error that makes a particular experimental outcome more or less likely.
Errors can happen in any experiment: people make mistakes in measurement, instruments fail, computer glitches can alter data. For example, relativity has been tested many times, so it is generally accepted as true, but there could be an instance, which has not been encountered, where it is not true. For example, a scientist can form a hypothesis that a certain type of tomato is red.
During research, the scientist then finds that each tomato of this type is red. Though his findings confirm his hypothesis, there may be a tomato of that type somewhere in the world that isn't red.
Thus, his hypothesis is true, but it may not be true percent of the time. Most formal hypotheses consist of concepts that can be connected and their relationships tested. A group of hypotheses comes together to form a conceptual framework. As sufficient data and evidence are gathered to support a hypothesis, it becomes a working hypothesis, which is a milestone on the way to becoming a theory. Though hypotheses and theories are often confused, theories are the result of a tested hypothesis.
While hypotheses are ideas, theories explain the findings of the testing of those ideas. Theories are structures of ideas that explain and interpret facts," said Tanner. In many cases, researchers might draw a hypothesis from a specific theory or build on previous research. For example, prior research has shown that stress can impact the immune system.
So a researcher might hypothesize: "People with high-stress levels will be more likely to contract a common cold after being exposed to the virus than people who have low-stress levels. In other instances, researchers might look at commonly held beliefs or folk wisdom.
The researcher might pose a specific hypothesis that "People tend to select romantic partners who are similar to them in interests and educational level. When trying to come up with a good hypothesis for your own research or experiments, ask yourself the following questions:. Before you come up with a specific hypothesis, spend some time doing background research. Once you have completed a literature review, start thinking about potential questions you still have.
Pay attention to the discussion section in the journal articles you read. Many authors will suggest questions that still need to be explored. In order to form a hypothesis, you should take these steps:. In the scientific method , falsifiability is an important part of any valid hypothesis. Students sometimes confuse the idea of falsifiability with the idea that it means that something is false, which is not the case. What falsifiability means is that if something was false, then it is possible to demonstrate that it is false.
One of the hallmarks of pseudoscience is that it makes claims that cannot be refuted or proven false. A variable is a factor or element that can be changed and manipulated in ways that are observable and measurable.
However, the researcher must also define how the variable will be manipulated and measured in the study. For example, a researcher might operationally define the variable " test anxiety " as the results of a self-report measure of anxiety experienced during an exam. A "study habits" variable might be defined by the amount of studying that actually occurs as measured by time. These precise descriptions are important because many things can be measured in a number of different ways.
One of the basic principles of any type of scientific research is that the results must be replicable. Some variables are more difficult than others to define. How would you operationally define a variable such as aggression? For obvious ethical reasons, researchers cannot create a situation in which a person behaves aggressively toward others. In order to measure this variable, the researcher must devise a measurement that assesses aggressive behavior without harming other people.
A scientific hypothesis can become a theory or ultimately a law of nature if it is proven by repeatable experiments. Hypothesis testing is common in statistics as a method of making decisions using data.
In other words, testing a hypothesis is trying to determine if your observation of some phenomenon is likely to have really occurred based on statistics. Statistical hypothesis testing, also called confirmatory data analysis, is often used to decide whether experimental results contain enough information to cast doubt on conventional wisdom.
For example, at one time it was thought that people of certain races or color had inferior intelligence compared to Caucasians. A hypothesis was made that intelligence is not based on race or color.
People of various races, colors and cultures were given intelligence tests and the data was analyzed. Statistical hypothesis testing then proved that the results were statistically significant in that the similar measurements of intelligence between races are not merely sample error.
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