Probability distribution of marks should not be normal.
What type of variable is the mark, discrete or continuous? Marks is a discrete random variable that has a finite number of values or a countable number of values. A continuous random variable has infinitely many values, and those values can be associated with measurements on a continuous scale in such a way that there are no gaps or interruptions. Requirements for a Probability Distribution 1. ΣP(x) = 1 where x assumes all possible values of marks 2. 0 ≤ P(x) ≤ 1 for every individual value of x For example, 2000 students gave exams with full marks of 10, the probability distribution of marks to have a normal like curve will have following frequency distribution given in the table. Marks x Frequency f Probability P(X=x) 0 4 0.002 1 23 0.0115 2 99 0.0495 3 227 0.1135 4 399 0.1995 5 497 0.2485 6 390 0.195 7 251 0.1255 8 84 0.042 ...