Hypothesis testing refers to the process of making inferences or educated guesses about a particular population parameter. This can either be done using statistics and sample data, or it can be done on the basis of an uncontrolled observational study. When a pre-determined number of subjects in a hypothesis test prove the "alternative hypothesis," then the original hypothesis (the "null hypothesis") is overturned.
Below, you will find some examples of hypothesis testing in a variety of different cases.
- A hypothesis is put forward that children who take vitamin C are less likely to become ill during flu season than those who do not. A hypothesis test is conducted where a sample group of children is given vitamin C for three months while another group is not. As it turns out, the alternative hypothesis is confirmed.
- Researchers conduct hypothesis testing that challenges the original assumption that aspirin can help a person who has a heart attack. Research is conducted confirming the null hypothesis.
- Several scientists observe that during the winter, a certain bird’s feathers become white, camouflaging these birds from predators. Hypothesis testing is conducted on a population of birds and discovers that indeed a significant number of the birds’ feathers do change color for the winter.
- A person claims to be able to see through walls, when the null hypothesis states that people cannot see through walls. Hypothesis testing is conducted where the person is asked to sit on one side of a wall and guess what objects are presented on the other side of the wall. The null hypothesis is proved correct.
- Most redheads, a hypothesis suggests, are insecure about their hair color. A hypothesis test is conducted wherein redheads are given polygraph testing to determine how they feel about their hair color. In the end, the alternative hypothesis is rejected when the data shows that most redheads are comfortable with their hair color.
- One scientist makes an alternative hypothesis that, contrary to popular belief, young boys are not necessarily prone to more behavioral problems than young girls. Testing confirms the alternative hypothesis – that young boys and young girls are often of similar temperament.
- Hypothesis testing of the conception that people with obese parents are likely to become obese themselves suggests that obesity has little to do with genetics. Data is generated on a sample population that confirms the null hypothesis that genetics do play a part in a person’s weight.
- An individual claims that, contrary to what is commonly accepted, he is telekinetic and can read minds. Research is conducted that indicates he cannot read minds, thus confirming the original null hypothesis.
- Accused of a grave crime, a person is placed under arrest and a trial is conducted. The null hypothesis, that he is innocent, is challenged in court. Data collected during the investigation demonstrates the alternative hypothesis that there is reasonable evidence to convict the individual of the crime.
- Hypothesis testing of the null hypothesis that being out in the cold weather can cause a person to get sick suggests that, in opposition to the old wives’ tale, an individual will not necessarily become ill by staying outside in the cold.
Hypothesis testing is very important in the scientific community and is necessary for advancing theories and ideas. Statistical hypothesis tests are not just designed to select the more likely of two hypotheses—a test will remain with the null hypothesis until there's enough evidence to support the alternative hypothesis. Now you have seen several examples of hypothesis testing and you can better understand why it is so important. For more information on types of hypotheses see Examples of Hypothesis.