1. Unit 2: Collecting Data & Survey Design The work of statisticians is highly valued as they provide everything needed by those coming from different background for various purposes. Such those are economy, education, interest, etc. But, the stasticians can not work without data. Survey: A method of gathering data from a group of individuals often conducted through telephone, mail or the web.

2. several methods to gather information Secondary data (e.g. data provided by the government, data by researchers, etc. Those data are avaliable for others such as www.data.gov). Its benefits are inexpensive & practical), while the drawbacks are not current and data may not answer the research question of interest).www.data.gov Primary data (e.g. personal interview, focus group, questionnaire-based survey, etc. These are conducted by those who work directly to get the data)

3. personal interview It involves one person directly interviewing another person It is conducted if the person interviewed is not likely to respond to other survey methods such as an online paper and pencil survey Its advantages: depth and comprehensive Its disadvantages: expensive, time consuming, yield small sample size

4. focus group to explore people’s ideas and attitudes towards an item of interest Often used to test new approaches or products and observer in real time, potential customer’s thoughts on the product. Usually conducted by a moderator, who leads a discussion with the group. The discussion is often observed by an outside party who records the reactions of the group to the product Its advantage: collect data a data yet to happen such as a new product or potential new advertising cmpaign Its disadvantage: unrepresentative group, invalid generalization, etc.

5. questionnaire-based survey It can be conducted through mail, phone and internet The researcher distributes the questionnaire to a group of people and wait for the repsonses to come back to be analyzed Its advantages: a cost effective, cover a wide geographic area, increase chances of having a representative sample Its disadvantages: a high rate of non-response and no opportunity to ask follow up questions

6. key principle to develop questionnaire Define goals & write questions Keep the questionnaires as short as possible Ask questions pertinent to your study Avoid questions only interesting to know A good question is clearly written and evokes a truthful, accurate response

7. Example good What kind of computer do you own? A.Accer B.Toshiba better What kind of computer do your own? A.Accer B.Toshiba C.Neither

8. Sampling Methods Sampling is the use of a subset of a population to represent the whole. Two main sampling methods are probability sampling and non-probability sampling Probability sampling: each person has a known non-zero probability of being sampled Non-probability sample sampling: members are selected in a non-random methodology

9. Probability Sampling Random sampling (each member of the population has an equal and known chance of being selected). Selection is done essentially picking out of a hat Stratified sampling (the population is divided by one or more characteristics and then random sampling is done within each divide. It is done where a researcher wants to ensure that specific groups of the population are selected in the sample. Systematic sampling (the researcher selects every “k”th member from an oredered list)

10. Non-probability sampling It is utilized when random sampling is not feasible (e.g. The population is hard to contact or identify) Example of non-random sampling is convenience sampling, judgement sampling

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