Hypothesis testing Flashcards
What is a research question?
When conducting a piece of scientific research, we are attempting to answer a research question. The research question provides the frame for the entire research project. Everything read, experimented and discussed should relate back to it. Research questions may be quite broad and non-specific, or narrow and specific.
What is a hypothesis?
A statement that predicts a new finding before the answer is known. A prediction of what the answer to the research question may be. Predictions are stated at the outset of a piece of work, and once data have been collected, carefully chosen statistical tests are able to test the validity of the hypothesis.
What are the 2 types of hypothesis?
Alternative hypothesis and null hypothesis.
Give an example of a method of evaluating the research question.
Hypothesis testing, often in combination with significance testing using statistics.
What is a null hypothesis?
H0 states that there is no dependent relationship between 2 variables. Most important hypothesis to test, as being able to reject it demonstrates the existence of a relationship. Not often referred to in scientific papers, probably because the authors and readers understand and appreciate its existence as tacit (i.e. doesn’t need to be specifically stated).
What is an alternative hypothesis?
The alternative hypothesis predicts a specific and reproducible relationship between variables.
Sometimes you may predict the direction of the finding, which is especially useful if the results of an experiment can only possibly go in one direction.
Although investigators might select a directional hypothesis, which predicts a change in only one direction, when it comes to analysing data it is good practice to check for changes in both directions, in case you miss an effect.
How is a null hypothesis rejected?
The hypotheses are stated at the outset of a piece of work, and once data have been collected, carefully chosen statistical tests are able to test the validity of the hypothesis. The statistical test is used to determine whether we can reject, or fail to reject, the hypothesis.
What is a p-value?
Statistical tests usually include a p-value in their output. The ‘p’ stands for probability: the likelihood that the observed difference (or something more extreme) was observed by chance.
The p-value returns a number between 0 and 1 that calculates the probability your observed results are real. A study based on a small group reflects what would be observed in the entire population. The p-value is interpreted – and used to reject or fail to reject the hypothesis – by comparing the calculated probability to the significance level, usually denoted as alpha (a).
What is the alpha (a-) value?
The probability of rejecting a null hypothesis when it is true. For example, a significance level of 0.05 indicates a 5% risk of concluding that a difference exists when there is no actual difference- rejecting the hypothesis when it should not be rejected.
