The concept of Null Hypothesis is a key concept of statistics. A hypothesis is an idea or tentative theory NOT supported by hard evidence, usually stating that some relationship exists between two variables. This hypothesis is usually referred to as H_{1}. The Null Hypothesis is the opposite statement, such as "there is NO relationship which exists between the two variables". It is this statement which is usually tested by statistical tools. The Null Hypothesis is usually referred to as H_{0}. Before you undertake a complex statistical calculation, you should always formulate the Null Hypothesis H_{0}. Your calculations will then show that:
Examples:
