Investigative and Practical Skills

The Null Hypothesis

The Null Hypothesis

null hypothesis

Statistical test can be used to find out the validity of a set of results. In other words, to find out if an observed pattern is real or simply chance. The result you get from a statistical test is in the form of a probability or P-value and on a scale of 0 to 1. The P-value is the probability of how many of the values observed were down to chance. Therefore, a low P-value means not many of the results were down to chance whereas a high P-value means a large number were down to chance.

In biology the cut-off used is 0.05% (5%).

  • If P ? 0.05 then the conclusion is that the observed differences are down to chance.
  • If P? 0.05 then the conclusion is that there’s a significant difference or correlation.

Before carrying out a statistical test a null hypothesis (H0) must be made. H0 always predicts that they’ll be no difference or no correlation. Statistics can be used to test a null hypothesis (H0). They can support or disprove the null hypothesis but not prove it. The null hypothesis is used as a testable hypothesis.

Your P-value is basically the probability that H0 is true.

  • If P ? 0.05 then the null hypothesis is accepted.
  • If P < 0.05 then the null hypothesis is rejected.