Stats 250 F16 Lecture Notes Chapter 2 - Stats 250 Lecture...

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Lecture Notes Page 25Stats 250 Lecture Notes 2: Sampling, Surveys and Gathering Useful Data Do not put faith in what statistics say until you have carefully considered what they do not say. ~ William W. Watt So far we have mainly studied how to summarize data - exploratory data analysis - with graphs and numbers. The knowledge of how the data were generatedis one of the key ingredients for translating data intelligently. We will next discuss sampling, how to conduct surveys, how to make sure they are representative, and what can go wrong. Collecting and Using Sample Data Wisely There are two main types of statistical techniques that can be applied to data. Definitions: Descriptive Statistics:Describing data using numerical summaries (such as the mean, IQR, etc.) and graphical summaries (such as histograms, bar charts, etc.). Inferential Statistics: Using sample information to make conclusions about a larger group of items/individuals than just those in the sample. In most statistical studies, the objective is to use a small group of units (the sample) to make an inference (a decision or judgment) about a larger group (the population). Definitions: Population: The entire group of items/individuals that we want information about, about which inferences are to be made. Sample: The smaller group, the part of the population we actually examine in order to gather information. Variable: The characteristic of the items or individuals that we want to learn about. One way to view these terms is through a Basket Model:
Lecture Notes Page 26Try It! Would it be Appropriate? For each situation explain whether or not the available data could be used to make inferences regarding the research question of interest. Do you think the data might be considered representative (considering the question of interest)? a.Research Question:Do a majority of adults in state support lowering the drinking age to 19?
b.Research Question:Do a majority of adults in state support lowering the drinking age to 19?

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