1. Source of data :
secondary sources 1.1 Data: Data is collected by someone else or experimental investigation of the way
the original information already exists on the original data we just re-processing, sorting, so that we can meet the needs of
the channel: [External ] statistics department, newspapers periodicals, the Internet; [internal] financial statements, internal company statistics
gathering secondary data is used by researchers first considered and it should start with the analysis of secondary data
on second-hand information to assess:
who is 1.1.1 data social gathering strength and credibility were collected
1.1.2 Why is the purpose of collecting data for internal interest groups is doubtful
1.1.3 data are collected in different ways how to get the data interpretation and persuasion is different
1.1. 4 when the data collection has a certain timeliness
direct 1.2 data sources: through its own investigation or experimental activities, direct access to first-hand data
is mainly obtained experimental investigation of the social phenomenon specific to natural phenomena through surveys and experiments
are usually faced with data samples ----> Generally drawn from a valid sample?
2. The survey data in two ways :
how to choose a good sample?
1. For research problem: not the same as different issues selected sample of ----> Satisfaction (who have been consumed); purchase intention (potential buyers)
in terms of cost and 2. the relationship between survey estimation accuracy: good sample has a certain price (cost savings); relax estimation accuracy (aerospace equipment and sausage, ratings and stock returns)
2.1 probability sampling : random sampling, also known [can calculate the estimated amount of error] means to follow the principle of random sampling in each unit has a certain chance to be elected sample
2.1.1 randomly drawn sample excluded consciously drawn out investigation unit just random ≠ subjective
probability 2.1.2 each sample is drawn is known or can be calculated
2.1.3 when the amount estimated by the overall standard sample to consider the probability of each sample was drawn of the estimated observations not only about the sample unit of its kind into the probability is also related to
simple random sampling, stratified sampling, cluster sampling, systematic sampling, multi-stage sampling.
2.2 Non-probability sampling : probability sampling with respect to the requirements in terms of data but taken according to the purpose of research are not random samples taken somehow extracting portion from the population analysis units
convenience sampling, sampling is determined, voluntary sample snowball sampling quota sampling,
2.3 probability sampling and non-probability sampling comparison:
What type of sampling taken in the investigation depends on many factors: the nature of the problem research questions, using the data to be described, the survey features, cost, time,
non-probability sampling results of the samples can not be used to estimate the corresponding parameters of the overall
probability sample selection sampling and data analysis are demanding higher cost of professional knowledge of statistical
non-probability sampling required expertise is not very high