N order to set rates, an insurance company is trying to estimate the number of sick days that full time workers at an auto repair shop take per year. Assume σ = 6.8 days. How large a sample must be selected if the company wants to be 98% confident that the true mean differs from the sample mean by no more than 2 days?

The  large  sample must be selected if the company wants to be 98% confident that the true mean differs from the sample mean by no more than 2 days

n = 62.5427≅63

Step-by-step explanation:

Step1:-

Given maximum of error = M.E =  2 days

Given population standard deviation  σ = 6.8 days

98% confident level Z₀.₀₂ = 2.326

Step2:-

we know that the maximum of error

cross multiplication , we get

squaring on both sides, we get

on calculation , we get

n = 62.5427

Conclusion:-

The  large  sample must be selected if the company wants to be 98% confident that the true mean differs from the sample mean by no more than 2 days

n = 62.5427≅63

step-by-step explanation:

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18