Internal validity the extent to which a study is methodologically sound free of

Internal validity the extent to which a study is

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Internal validity: the extent to which a study is methodologically sound; free of confounds and lead to valid conclusions External validity: the extent to which a study’s findings can be generalized beyond the study itself; typically use samples representative of the population What is correlational research? Why is it important? Understand the concept of causation and how it relates to correlational research. What does a correlation coefficient tell us? What is the difference between positive and negative correlation? Correlation: the degree to which events or characteristics vary with each other o Used to determine the “co-relationship” between variables Advantages: has high external validity (can generalize findings), can repeat studies on other samples Difficulties: lack internal validity; results describe but do not explain a relationship; results say nothing about causation Positive correlation: variables change in the same direction; slope is upward and to the right Negative correlation: variables change in the opposite direction (downward slope) Unrelated: no consistent relationship (no slope) Magnitude (strength) o High- variables which vary closely together; fall close to the line of best fit o Low- variables which do not vary as closely together; loosely scattered around the line of best fit
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Correlation coefficient- calculated numerically “r”; can vary from +1.00 (perfect positive correlation) to -1.00 (perfect negative correlation) o Sign indicates direction o Number indicates magnitude Can be trusted base on statistical analysis of probability o Unlikely to have occurred by chance- if there is less than a 5% probability that findings are due to chance, results are considered statistically significant o Confidence increases with the size of the sample and the magnitude of the correlation Do we find perfect correlations between variables in psychological research often? Most correlations fall far short of “perfect” What is an effect size ? Reflects the size of association of variables Independent of sample size Used to compare the strength of findings from different studies Can’t use significance to compare findings if sample sizes were different Size of zero means there is no association between the variables Distinguish between a retrospective and prospective strategy in research. Retrospective: involve looking back in time, often to a point before the participant developed a disorder Prospective: involve looking ahead in time, usually with participants with a high likelihood of become disordered Understand features of experimental method. Be able to identify an independent and dependent variable. Scientists control all factors except the independent variable Actively manipulate independent variable If dependent variable changes as independent variable changes, it is regarded as a cause of the outcome Be able to identify and explain an ABAB design. Why are these designs so helpful?
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