NCERT Exercise 13.2 Q9 - Statistics
Question: For heights 70-75, 75-80, ..., 110-115 with frequencies 3, 4, 7, 7, 15, 9, 6, 6, 3, find mean, variance and standard deviation using the short-cut method.
Answer: Use class marks and a coded-deviation table; report mean, variance and the positive square root.
Full step-by-step NCERT solution with diagrams on Something by Zero.