Một ủy ban an toàn kiểm tra ngẫu nhiên 900 công nhân xây dựng trong thời gian làm việc, thấy có 48 công nhân không mang mũ bảo hộ. Hãy ước lượng tỷ lệ công nhân không mang mai bảo hộ trong thời gian làm việc với độ tin cậy 98%

The percentage of workers not wearing the helmets is 5.3 %.

Step-by-step explanation:

A safety committee randomly examined 900 construction workers during their work, and found that 48 workers were not wearing helmets. Estimate the percentage of workers who do not wear protective masks during their working time with 98% confidence

total workers = 900

Not wearing helmet = 48

Percentage which are not wearing the helmets

= %

there are lots of ways.   pick's theorem tells us if the vertices are lattice points the area a is

a = b/2 + i - 1

where b is the number of boundary lattice points and i is the number of interior lattice points.

in the figure i count b=16, i=50 so

a = 8 + 50 - 1 = 57

let's try the shoelace formula.   the area is half the sum of the cross products of the sides.  

a(-2,6)   -2(2)-6(-5) = 26

b(-5,2)   -5(-3) - 2(-2) = 19

c(-2,-3) -2(-3) - (-3)(4) = 18

d(4,-3)   4(3) - (-3)(5) = 27

e(5,3)   5(3) - 3(1) = 12

f(1,3)     1(6) - 3(-2) = 12

a(-2,6)

each of the cross products is twice the area of the triangle with the associated side and one vertex the origin. so the area of abo=26/2=13.

area = (1/2) (26 + 19 +   18 + 27 + 12 + 12) = 57

that checks!