"Sampling technique" end review

• Category sampling:
  non-probability sampling and probability sampling.
  • Non-probability sampling: not in accordance with the principle of random when taking a sample.
    Example: Analyzing a sample, to facilitate sampling, sampling voluntary, quota sampling.
    A convenience sample, also known as random sampling, not a random sample.
    Advantages: simple operation, no sampling frame, economical, fast, survey data processing is easy.
    Disadvantages: sampling errors can not be calculated, the error can not be controlled from a probabilistic sense, the overall sample data can not be inferred, the presence of systematic error checking unit.
  • Probability sampling: Also known as random sampling, according to the random principle, in accordance with the pre-designed procedures, sampling methods section units drawn from the population.
    • Features:
    1. According to a certain probability of randomly drawn sample. (Randomly, when taking a sample intentionally excluded extracting unit subjective investigation, so that each cell has a certain probability of being drawn)
    2. Each cell is drawn probabilities are known, or can be calculated out.
    3. When the sample is estimated by the amount of the overall goal, the need to consider the kind of probability sample.
    • Probability sampling advantages:
      can obtain the estimate of the overall objective variable depending on the sample, and can calculate the amount of each estimated sampling error, thus the reliability of the overall objective variables inferred. The precision may be required to calculate the amount of sample required.

Role sample survey:
cost savings. Time-sensitive. Can undertake a full investigation can not be qualified projects. Help to improve the quality of survey data.