Error Types & P Value Flashcards
What is the p value?
The p value is the probability of obtaining a result by chance at least as extreme as the one that was actually observed, assuming that the null hypothesis is true.
What is a type 1 error?
The null hypothesis is rejected when it is true.
Also termed alpha.
(i.e. showing a difference between two groups when it doesn’t exist - a false positive)
What is a type 2 error?
The null hypothesis is accepted when it is false.
Remember accepted has 2 conjoining letters.
This is also known as beta.
(Failing to spot a difference when one really exists - a false negative)
What are the 2 types of hypothesis that are tested and what do they state?
A null hypothesis (H0) states that two treatments are equally effective.
Alternative hypothesis (H1) is the opposite of the null hypothesis, i.e. There is a difference between the two treatments
What is the purpose of using significance tests?
A significance test uses the sample data to assess how likely the null hypothesis is to be correct.
Which error type is affected by sample size?
Type 2 errors are affected by sample size.
Type 1 errors are not.
What is the power of a study?
The power of a study is the probability of (correctly) rejecting the null hypothesis when it is false, i.e. the probability of detecting a statistically significant difference.
Power (1 - beta)
How can the power of a study be increased?
Power can be increased by increasing the sample size
