Determination of Samples in Research

A. Sample Definition
The sample is an example, a monster, representan or representative of a population that is large enough in number or one part of the overall selected and representative nature. Sample collection activity is called sampling.
While the population is totatlitas all cases, events, people or things. Can be either a number of human population, curriculum, management, teaching tools, teaching, events. Of all the population must be affirmed / found in the characteristics or attributes when the population will be the object of research.
The aim of researchers took samples are obtained information about the object of research by observing only a part of the population. This is done because of various factors to consider.
B. Sampling reason
Sampling was done because it is often not possible researchers looked at all the members of the population is relatively large in number (one by one observed). For example, researchers might not taste the fruit of rambutan as much as a truck that will be studied. However, the main requirement is a representative sampling of the population. Some of the reasons for withdrawal the sample is:
1. population size (some are very large even infinite)
2. Time, effort and cost.
A. Sampling Ways
1. Random Sampling Technique
a. Simple random sampling, where the free sample are random. Technique is used when the sample homogeneous.
b. Use of Random Numbers Table
1) Each member of the population be numbered.
2) Define the random numbers in the table (statistics).
3) Determine the criteria of the decimal.
4) Determine the beginning of the selection of random numbers.
5) Select the number indicated.
1. Non-Random Sampling Technique
In this technique, not all members of the population gets a chance to be sampled. There are three types of samples of these categories, namely:
a. Incidental samples (haphazard) example will be investigated in 100 students UPI. Researchers come to campus to find 100 students. Thus, students who studied were discovered by researchers on campus.
b. Sample quota (quota) This technique is similar to the incidental campus, just prior to the first sampling was made according to sample category strata, and each stratum was allotted.
c. Purposive sample (destination) technique is used based on the consideration of researchers tertetntu (subjective). For example, researchers want to know that students are learning how to regularly have high achievement. Then researchers took samples only students who regularly study and high achievement.
A. Determining sample size
In principle there is no standard rule how many percent of the sample should be taken from a population. But according to the research literature generally argues that the sample that exceeds better than the disadvantages. That means it would be better as much as possible of the population. For the population of 10-100 should be taken one hundred percent (100%). On top of 100-300 can be taken 70% and above 1000 is taken 20%.
If the sample is only 10 so to find the correlation between variables X with Y to risk the possibility of lost 5% and require a 0.632 correlation numbers (see the count statistics), whereas if 100, then the necessary number of correlation 0.195. to meredusir error should be given strict requirements, especially the small sample.
B. Factors to Consider In Sampling
1. Total population and its characteristics according to the variables studied.
2. Significance level in making estimates.
3. An upper limit of sampling error.
4. Research objectives, instruments and data analysis that will be used.
5. Available resources (cost, time, energy)