Sampling plan for raw materials (WHO guideline)

(1) n Plan : n =1+√N ( n: simply rounding )
(2) p Plan : p = 0.4√N ( p: rounding up to the next highest integer.)
(3) r Plan : r = 1.5√N ( r: rounding up to the next highest integer.)

based on the table above,
in n-plan’s case, it says n=4 when N=7~13.
but, by my calculation, if n=13,
1+√N = 1+√13 = 1+3.60555 = 4.60555.
so if simply rounding 4.60555, shouldn’t it be 5?

but I don’t understand why the table says n=4, not 5 ???

could anyone help me, please ? :slight_smile: