1. S AMPLING T ECHNIQUES

2. How is it possible that when survey’s come out, they can say that 23% of Canadians like to take long walks on the beach when no one ever asked for my opinion???? Researchers usually take surveys of smaller groups and then apply those results by estimating the opinions of the entire population. Example  a survey was done using this class to determine what was the best soft drink. These result were then used to represent the entire school.

3. Population refers to all individuals who belong to a group being studied. (the school pop.) Sample refers to the class in which the results were obtained. The population depends on the kind of data being collected. Who would the population be? - What is the best type of lipstick to wear? Pop. – women….or women who wear lipstick.

4. If the population is small, it is easy to survey the entire group. If it is too large, a SAMPLING FRAME will have to be selected. – a group of individuals who actually have a chance of being selected. How do we know how many people to select?

5. Simple Random Sample – every member of the pop. has an equal chance of being selected. The selection of any particular individual does not affect the chances of any other individual being chosen. This can be done by drawing names randomly or assigning numbers and then using a random-number generator to determine what number to choose. Systematic Sample – go through the population sequentially and select members at regular intervals. The pop. size and sample size determine the sampling interval. Interval = population size / sample size.

6. Ex. A newspaper is planning on a marketing survey of its 825 000 customers. For financial reasons, the company will only sample a size of 350. Suggest a method for selecting a systematic sample. Determine the sampling interval. Interval = 825 000 / 350 = 2357 Pick someone within the first 2357 people on the list and then choose every 2357 th customer from that point on. For simplicity sake, you could choose every 2300 rd person.

7. Stratified sample – includes groups of members who share characteristics, such as gender, age, or education level. Such groups are called STRATA. A stratified sample has the same proportion of members from each stratum as the population does. How would we be able to survey 25% of the student body in this school, making sure that we have the same proportion of students from each grade? Take 25% of each grade to make up the entire population.

8. Cluster Sample – if the sample groups are representative of the entire population, then you can just survey those people. Ie employees of a chain.  since they would all have the same interests, you can just sample from select restaurants instead of the entire chain. Multi- Stage Sample – Start by randomly selecting from a larger group and then randomly select from that group, and so on, making each selection criteria more specific each time.

9. Voluntary – Response Sample – invite any member of the population to participate in the survey. The respondents are not always representative of the entire population. Example  university research. Convenience Sample – the sample is easily accessible. Homework Pg 117 # 1abc,2abc,3ab,4,6,8,9