Question

Please answer all parts, it is not that lengthy. If you can't answer last parts, don't attempt then . Leave for someone else

A manufacturing process produces defective items 15% of the time. A random sample of 80 items is taken from the 3000 produced on a particular day, and each sampled item is tested to see if it is defective or not.
In the context of this problem, identify each of the following:
a. Population:
b. Parameter of interest:
c. Sampling frame:
d. Sample:
e. Sampling method:
f. Is there any potential bias? Explain your answer.

Answer 1

a. Population: All items produced by the manufacturing process can be said as our target population.

b. Parameter of interest: Number of defective items produced in these 3000 units is our parameter of interest which we try to estimates by obtaining the number of defectives from the sample of size 80.

c. Sampling frame: The list of items of the population from which the sample is drawn is the sampling frame.

So here the sampling frame is 3000 items produced by the manufacturing process in a single day.

d. Sample: the 80 items selected randomly out of 3000

e. Sampling method: Simple random sampling.

f. Yes. There can be a potential bias. As we are sampling out of the units produced on a "single day" to conclude the defective number of items produced by the manufacturing process in general.

On a single day, the manufacturing process may be subject to many uncertainties that could lead to better or worse performance than other days. Sample from different days could have been selected.