Null hypothesis

The null hypothesis (kimu kasetsu) is the hypothesis in statistical hypothesis testing that takes the position that the results of an experiment or survey arose by chance. Specifically, it refers to the premise that the phenomenon the researcher wants to test does not exist, or that there is no particular effect or relationship. The null hypothesis serves as the baseline against which its validity is evaluated using actual data. For example, when comparing the effects of Treatment A and Treatment B, the null hypothesis takes the form "there is no difference in effect between Treatment A and Treatment B." If the null hypothesis is rejected, the researcher concludes that the new hypothesis (the alternative hypothesis) is likely to be supported.