A p-value is the probability of seeing a result at least as extreme as yours if the null hypothesis were true, that is, if there were no real effect in the wider population. A small p-value means your sample result would be unlikely under that assumption, so you treat the effect as statistically significant. A p-value is not the probability that your hypothesis is true, and it is not a measure of how large the effect is; it only tells you how surprising the data are if nothing is going on.
What the threshold actually decides
The familiar cut-off of .05 is a convention, not a law of nature. It sets your tolerance for a false positive, the risk of declaring an effect that is not really there. Choosing alpha of .05 means you accept a one-in-twenty chance of that error before you ever see the data. Some fields demand a stricter .01 because the cost of a wrong claim is higher. The threshold is a decision rule you commit to in advance; moving it after you see the result is one of the surest ways to lose your supervisor's trust in your dissertation.
What a p-value does not tell you
The most common misreadings cost marks. A p-value of .04 does not mean there is a ninety-six percent chance your hypothesis is correct, and a p-value of .20 does not prove the null hypothesis is true; it only means you lack the evidence to reject it. Crucially, significance is not size. With a large enough sample, a trivial difference will cross the threshold, which is why a p-value must always be reported next to an effect size that shows how big the effect is. The p-value answers "is it likely real?", never "does it matter?".
Reporting the value honestly
Report the exact p-value rather than just "p < .05" wherever you can, because a value of .049 and a value of .003 carry very different weight even though both clear the threshold. Treat a result of .055 as what it is, just over the line, and discuss it as suggestive rather than dressing it up as significant. Pairing the p-value with a confidence interval for the effect gives the reader far more than a bare significance flag, and the formatting rules for all of these numbers live in how to report statistics in APA style.
| p-value | How to read it |
|---|---|
| Below .01 | Strong evidence against the null hypothesis |
| Below .05 | Conventionally significant; report the effect size too |
| Around .05 to .06 | Borderline; describe as suggestive, not significant |
| Above .10 | No evidence to reject the null; not proof it is true |
Where the p-value sits in your analysis
A p-value is the last step of an inferential test, not the whole story. It arrives only after you have chosen the right test, checked its assumptions, and computed a test statistic, which is the path traced in the move from descriptive to inferential statistics. Read in that context, the p-value becomes a disciplined yes-or-no on a single, pre-stated question rather than a magic number. Reported alongside its effect size and confidence interval, it gives your results chapter the honesty examiners reward.