A continuous, symmetrical, bell-shaped frequency distribution for variable data. Data distribution is symmetrical around the mean and there is an equal chance of a data point being above or below the mean. A normal distribution can be described completely by knowing the mean and standard deviation.
A statement of no change or difference. This statement is assumed true until sufficient evidence is presented to reject it; “if p is low, H0 must go”. The null hypothesis is what you are trying to disprove.