There are the statistical analyses that weigh up the differences that were found in the data.
The results of the analyses are presented in many ways, but usually a p value is reported.
This is the probability that the differences found were due to chance.
If the p value is less than 5 per cent (usually written as p < 0.05) then the differences are said to be statistically significant.
In other words, they are not due to chance.
Remember statistical significance has a precise statis‒ tical meaning of something not being due to random chance alone.
‘Significant’ results are not necessarily important, newsworthy or exciting (although the researcher who found them probably feels that they are).
So when writing essays about research, be careful to be clear about which sense of the word you are using.
In science, we can never really prove that a theory is true.
This may sound pessimistic, but it is an essential part of the scientific method.
All we can do in science is use evidence to reject or falsify a hypothesis or a theory.
An experiment is like an axe: all it can do is chop things down.
Experiments never directly prove that a theory is right; all they can do is provide indirect support by rejecting all the other theories until only one plausible theory remains.
For example, sometimes you hear people say things like ‘evolution is only a theory: science has never proved it.’ Well, that’s true, but only in the sense that science never proves that any theory is positively true.
But what the theory of evolution has done is assemble an enormous amount of convincing data proving that other competing theories are false.
So though it hasn’t been ‘proved,’ overwhelmingly, evolution is the best theory that we have to explain the data we have.
And that’s as good as we get with the scientific method.