Pronunciation: [nˈʌl ha͡ɪpˈɒθəsˌiːz] (IPA) 
The spelling of "null hypothesis" can be a bit tricky. The first word, "null", is pronounced /nʌl/, with a short "u" sound like "uh" and a clear "l" at the end. The second word, "hypothesis", is pronounced /haɪˈpɒθɪsɪs/, with a long "i" sound like "high", a stressed "o" sound like "ah", and a clear "s" at the end. The plural form, "null hypotheses", adds an extra syllable and is pronounced /nʌl haɪˈpɒθɪsiːz/.
A null hypothesis refers to a statement or assumption in statistics that is tested against an alternative hypothesis in order to determine the validity of the alternative hypothesis. The null hypothesis represents the default position or assumption that there is no statistical relationship or difference between variables or groups being examined.
In other words, it assumes that any observed difference or relationship is simply due to chance or random variation in the sample data rather than indicating a true effect or relationship in the population. The null hypothesis typically states that there is no significant difference, association, or effect between variables or groups under investigation.
When conducting hypothesis testing, researchers start by assuming the null hypothesis is true and collect sample data to evaluate its validity. Statistical tests are then employed to determine the likelihood that the observed data supports the null hypothesis. If the obtained data shows a low probability of occurring under the null hypothesis (typically defined by a predetermined significance level), the null hypothesis is rejected in favor of the alternative hypothesis, which suggests the presence of an effect, relationship, or difference. On the other hand, if the observed data does not provide sufficient evidence to reject the null hypothesis, it is retained as the most plausible explanation. Null hypotheses play a crucial role in hypothesis testing as they help researchers outline their research question objectively and assess the validity of alternative hypotheses.
The term "null hypothesis" was coined by the British statistician Ronald Fisher in the early 20th century. The word "null" originates from the Latin word "nullus", meaning "none" or "no". In statistics, the null hypothesis essentially states that there is no significant difference or relationship between variables or groups being compared. Fisher used the term to describe the default assumption or starting point that researchers aim to either accept or reject based on statistical evidence. Over time, the term "null hypothesis" has become a fundamental concept in statistical testing and hypothesis-driven research.
