The p-value is computed assuming the null hypothesis, no difference or no effect, is true. A small p-value, conventionally below 0.05, means the data would be surprising under that assumption, so the null is rejected. It is not the probability that the null is true, and it says nothing about how large or important an effect is: with 10,000 wafers, a 0.1 nm difference can produce a tiny p-value.
p is 0.21 on the liner split, so we can't call a difference. Doesn't prove they're the same either.
Also heard as
- p
- significance probability
Related terms
Significant
Describes a result unlikely to have come from chance alone at a stated risk level, which is not the same as important.
Power
Probability that a test will detect a real effect of a given size, set by sample size, noise and alpha.
t-test
Test that compares a mean against a target, or two means against each other, using the t distribution.
Confidence interval
Range calculated from sample data that brackets an unknown parameter, such as a mean, at a stated confidence level.
Fishing expedition
Analysis that tests many variables or subsets in search of any significant result, almost guaranteeing a false positive.