The age number of the students of a class are 15, 17,18, 20, 22, 24, 21, 17, 16, 15, 21, 22, 23, 22, 17, 22, 18, 22, 19 and 20. What will be mode of the series?

A. The central limit theorem B. The law of statistical regularly C. The law of inertia of large numbers D. None of the above

A. Sampling error B. Measurement error C. Coverage error D. Non-response error

A. Both (A) and (R) are true B. (A) is true, but (R) is false C. (A) is false, but (R) is true D. Both (A) and (R) are false

A. 0 B. 1 C. 0.4 D. 0.8