KEY FEATURES: Introduces students to developing research questions and shows their importance in driving research design. Rarely taught topics, such as how to enter and clean data, offer students information missed in both research methods and statistics courses. Shows how to write up survey results for academic, business and nonprofit reports to alleviate the confusion students feel about how to write up findings. Rigorous treatment of sampling focuses on many sampling issues from probability theory to weighting. Offers the process of actually conducting a survey with advice on administering surveys, incentives, and improving response rates.

# What Is Sampling Theory?

### What Is Sampling Theory?

We are interested in characteristics about the population, like income, for example. We don’t know the average income of the population, however. So, when we collect a sample of the population and take the mean (average) income of the sample, we do not know how well it reflects the population mean income.

Let’s say we draw a sample of size n, take the mean income from the sample, and toss it back. Then choose another random sample of size n, take the mean of income, and toss it back. Sampling theory tells us that if we do this an infinite number of times, and plot all the sample mean incomes, we would eventually get a bell shaped distribution (see Figure ...