Question

Suppose a purchasing manager wants to determine the average cost of machined metal parts in the US. How many machined metal parts would they have to sample? The manager wants to be 90% confident with a margin of error of 6.74. Suppose that the costs of the metal parts ranges from 93 to 220. When entering the values into JMP, round the planning value for the standard deviation to four values after the decimal. Round final answer as you normally would.

Answer 1

Answer:

they will have to sample 60 machined metal parts

Step-by-step explanation:

Given that;

Margin of Error E = 6.74

at 90% Confidence Interval, z = 1.645  { from table }

Range R = maximum range - minimum range = 220 - 93 = 127

standard deviation σ = R / 4 = 127/4= 31.7500

How many machined metal parts would they have to sample n = ?

to get our sample size, we use the following formula

n = [ zσ / E ]²

we substitute in our values

n = [ 1.645 × 31.7500 / 6.74 ]²  

n = [ 52.2287 / 6.74 ]²  

n = [ 7.7490 ]²          

n = 60.047 ≈ 60  

Therefore, they will have to sample 60 machined metal parts