INTRODUCTION TO ECONOMETRICS II ECO 306 NOUN 22
i. Element: An element is an object
on which a measurement is made,which
could be a voter in an area, a product as it comes off the assembly line or a plant in afield that has either flowered or not.
ii. Population: A population is a collection of elements about which we wish to make an inference. The population must be clearly defined before the sample is taken.
iii. Sampling units: These are some overlapping collections of elements from the population that covers the entire population. The sampling units partition the population of interest. The sampling units could be households or individual voters.
iv. Frame: Is a list of sampling units.
v. Sample: This is a collection of sampling units drawn from a frame or frames. Data are obtained from the sample and are used to describe characteristics of the population. Two advantages of sampling are that the cost is lower and data collection is faster than measuring the entire population.
vi. Census: The enumeration of the total element of the population.
Example 1: Suppose we are interested in what voters in a particular area think about the drilling of oil in the national wildlife preserves. The elements are the registered voters in the area. The population is the collection of registered voters. The sampling units will likely be households in which there maybe several registered voters. The frame is a list of households in the area.
1.1.3.4.2 Reasons for sampling Information could be obtained by taking a complete enumeration of the whole population or aggregate. This is usually difficult as information on every element is rarely available. Therefore, it is better to employ sampling method to obtained information than complete enumeration
for the following reasons i. Reduce cost: if data are secured from only a small
fraction of the aggregate, expenditures are smaller than if a complete census is attempted. With large populations result accurate enough to be useful can be obtained from samples that represent only a small fraction of the population.
