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Correlation

Review from statistics

whitley
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Correlation

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    1. Correlation

    2. Review from statistics… What is a correlation? Different types: Pearson, Spearman, point-biserial, phi Range of possible values Information it gives: Direction of relationship Strength of relationship Coefficient of determination

    3. What if it’s just due to chance, though? Null hypothesis? Role of p value Larger (farther from zero) test statistic, smaller the p Magical comparison value: alpha Relationship between alpha and critical test statistic

    4. The need for more than one participant Why can’t a single participant be used? Restricted range issues

    5. Correlation as a type of research design Correlation refers to a type of statistic, to find out about a particular relationship between two variables Also used to refer to a type of research design Frequently used interchangeably with non-experimental (for simplicity, though, use to refer to designs where could use a correlation to test hypothesis) In contrast to single subject designs we talked about – no manipulation involved

    6. Disadvantages of correlation Mantra: Correlation does not equal causation What does it mean? Why does it exist? Third variable problem: some non-measured variable is responsible for the association between two other variables E.g., birth control and toaster ovens in Taiwan in the 70’s Selection bias: similar to third variable problem: type of person who puts himself or herself in a certain situation E.g., incidence of respiratory illness in AZ

    7. Applying all this Bring out worksheet you brought in In pairs, complete it, and turn it in You can write on it, or you can re-download the worksheet at the computers, type your responses, and email it to me.

    8. Why use correlation at all, then? Advantages of correlation? Can examine association between things that cannot, or should not (think back to ethics!), manipulate

    9. Putting this into practice… As a class, will design and conduct correlational study As individuals, will write up the results of that study in APA style

    10. How to get started? First thing to do: figure out a topic Should just be one variable Should be in the form of a question Not a yes/no question Should be very broad Not yet a hypothesis Will then look to previous research to narrow down to a hypothesis

    11. Types of questions suited to correlation design What’s related to sorts of questions… What’s related to marital satisfaction? What’s related to happiness? What’s related to a long life-span?

    12. To do now Think of areas that interest you Think back to the areas you examined Thurs, Feb 5 Think about the research you found on those areas Do so more searches, for other research, and on topics that you may not have thought of Narrow down to one or two general topics you might be interested in Big commitment – we’ll be using the topic we decide on for each of the 3 class research projects, and you’ll be writing two papers on it

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