Questionnaire Sampling and Terms Terms Terms Population Bias

Questionnaire Sampling and Terms

Terms

Terms Population Bias the whole group being studied Relates to the method used to select the sample. Unbiased methods give all elements of population equal chance of selection. Sample A carefully selected subset of the population Representative A sample that bears similar characteristics and proportions to the population Sampling frame The list that gives information about the population – the source material for selecting the sample.

Population: a set which includes all measurements of interest to the researcher Sample: A subset of the population

Why sampling? Get information about large populations ê Less costs ê Less field time é More accuracy i. e. Can Do A Better Job of Data Collection î When it’s impossible to study the whole population

Simple random sampling

Systematic sampling Always picking a person at random based on the position of their name on a list. Start with a random number for the first selection point. Divide the total number in the set by the sample size you wish to use in your evaluation For example: If you want a sample of 30 and you have 180 pieces of data, 180/30 = 6 - pick every 6 th person in the list

Systematic sampling

Sampling Method Simple Random Systematic Sampling of Volunteers How Advantages Disadvantages Each member of the population is assigned a random number. Random numbers are drawn Each member of the population has an equal chance of being chosen. Is representative and unbiased Time-consuming and expensive The population is listed and then a sample is chosen using a pattern such as choosing every kth member Quicker and cheaper than random sampling If there is a repeating pattern in the population the sample may not be representative. The level of sampling errors cannot be determined People ask to be part of the sample Very quick and cheap Biased and not representative

Precision Cost

Circles – representative? Click on flower for sample selection app

Design In this section comment of the order of the questions and on the purpose of each question. Set up a table to help set out your work. Question Type of Question 1. Gender M/F? Multiple choice Purpose/reason There are only two options and it will be quick and easy for the participant to respond. It will also be easy for me to collate how many males and females once the survey’s are returned. 2. 3. I have chosen to put the questions in this order because…. .

Pilot survey In this section you will need to provide the drafted questions to another student. You will give written feedback to the writer of the questionnaire. Here is an example of the kind of feedback you could give. Question Number Feedback 1 This is a good simple question to start with and I agree multichoice seems like the obvious choice. 2 I noticed you only gave four options for this question and I’m wondering if you need to consider…. . 3 This open ended question is quite early in the questionnaire and I wonder if you could be left to the end. I also think you will get a vast range of answers that will be difficult to compile once all the survey’s are returned.