Bi weekly Assignment 4 – Data Collection

This assignment requires that you summarize how you will collect the data you will use for your research project.  There are several types of data available.  

Data Collection

Science is an empirical enterprise.  That means that it is data based.  There are two ways that we collect data:

• we observe people and use our observations as data, and
• we ask people questions and use what they tell us as data.

Sometimes surveys are referred to as sample surveys because we select a sample of individuals from the population and ask them questions.  Then we use their answers to these questions as our data.  Surveys can take various forms:

• in-person interviews,
• mailed questionnaires,
• telephone surveys, and
• web-based surveys.

Error is inevitable whenever we study something.  Since we can’t eliminate all error our goal is to minimize error.  Error can enter into a survey in various ways.

• Sampling error occurs when we select a sample from a population.  No sample is a perfect representation of a population.
• Coverage error occurs when the list of the population from which we select our sample does not perfectly match the population.  For example, about 98% of all households in the United States have a telephone (either landline or cell or both).  So when we do a telephone survey we fail to cover about 2% of all households.
• Nonresponse error occurs when we fail to reach the entire sample.  This type of error can occur in two ways – refusals and the failure to contact some individuals in the sample.
• Measurement error occurs when our measures of some concept fall short in some way.  For example, the way we word our survey questions can introduce error.  It turns out that it matters a great deal whether we refer to global warming or climate change when we ask people questions.

Our survey design should clearly describe how we plan to collect our data.  We should consider the different ways that error might enter into the data and how we will try to minimize that error.