Introduction to Business Management: Statistics Class 1. Topic 2. Types of sampling methods.
Planned 1. 1 Basic concepts of sampling. 1. 2 Types of sampling methods. 1. 3 Assess the quality of the sample. Survey error.
1. 1 Basic concepts of sampling Sampling provides a means of gaining information about the population without the need to examine the population in its entirety.
Sample Design Sample design covers the method of selection, the sample structure and plans for analyzing and interpreting the results. Sample designs can vary from simple to complex and depend on the type of information required and the way the sample is selected.
Sample Design What is necessary for sample design development: § § define target population calculate population size and a frame define a sample size select sampling method A sampling frame is a list of all units in your population.
1. 2 Types of sampling methods Sampling Methods Probability Samples Non-Probability Samples Simple Random Sample Stratified Sample Cluster Sample Systematic Sample Convenience Sampling Judgment Sampling Quota Sampling Snowball Sampling
Simple random sampling Definition: Ensures every member of the population has an equal chance of selection. l Produces defensible estimates of the population and sampling error. l Simple sample design and interpretation. l Need complete and accurate population listing.
Stratified Sampling Definition: The population is sub-divided into homogenous groups, for example regions, size or type of establishment. The strata can have equal sizes or you may wish a higher proportion in certain strata. l Ensures units from each main group are included and may therefore be more reliably representative. l Should reduce the error due to sampling. l Selecting the sample is more complex and requires good population information. l The estimates involve complex calculations.
Systematic Sampling Definition: After randomly selecting a starting point in the population between 1 and n, every nth unit is selected, where n equals the population size divided by the sample size. l Easier to extract the sample than simple random. l Ensures cases are spread across the population. l Can be costly and time consuming if the sample is not conveniently located. l Can’t be used where there is periodicity in the population.
Cluster Sampling Definition: Units in the population can often be found in geographical groups or clusters eg. schools, households etc. A random sample of clusters is taken, then all units within those clusters are examined. l Quicker, easier and cheaper than other forms of random sampling. Does not require complete population information. l Useful for face-to-face interviews. l Works best when each cluster can be regarded as a microcosm of the population. l Larger sampling error than other forms of random sampling. l A larger sample size may be needed to compensate for greater sampling error.
Reporting the results When reporting the results of a sample it is important to cover several key facts: § § § the sample size; the sample selection methodology; the estimates resulting from the sample, and the precision and confidence intervals for the estimates.
1. 3 Assess the quality of the sample. Survey error Nonsampling errors are errors that result from the survey process (inaccurate responses, bias in a selecting of individuals). Sampling error is the error that results from using sample to estimate information regarding the population (underrepresented population in a frame, nonresponse, interviewer error, questionnaire design).
Assess your understanding l l l True or false: A simple random sampling is always preferred because requires a smaller sample size. Which sampling method does not require a frame? The process of using sample statistics to draw conclusions about true population parameters is called A) statistical inference. B) the scientific method. C) sampling. D) descriptive statistics.
Course content 2. Sampling methods 1. Data Collection 5. Basic Probability 4. Variation 3. Data Visualization 7. Sampling 6. Probability Distributions Final Test
Home Assignment #1 Describe in one-page essay (200 -250 words) definitions, ways of use and limitations for one of these sample methods. Give an example using free data from the open source. l Simple Random Sampling l Cluster Sampling l Systematic Sampling l Stratified Sampling l Snow Ball Sampling l Quota sample Best essays (2 -3) will be posted to the common course materials folder and included into final test questions.
Скачать презентацию Introduction to Business Management Statistics Class 1 Topic
Topic 2.Sampling methods.ppt