Null Hypothesis?

Question

Can someone explain what a Null Hypothesis is?

Answer 1

The null hypothesis is a positive assertion that says what you believe to be true does not exist or has no effect. You must accept the null hypotheses unless there is sufficient evidence to refute it and thus have sufficient evidence for your original assertion.

An example would be: The radio signal I am detecting contains non-random components. The null hypothesis would be: The signal I am detecting is noise.

It is often used to remove bias, in that since it is difficult or impossible to prove a negative, you cannot assume an assertion to be even partly true by default. You must show that it is likely to be true because the null hypothesis is likely to be false.

Statistically, the Alpha level is the probability of being wrong when you reject the null hypothesis. As generally accepted, the alpha level must be less than 0.05 to show there is any validity to your assertion. Than means that there is a 5% chance or less that the null hypothesis is correct.