Elementary Statistics for AP Psychology (page 3)

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By — McGraw-Hill Professional
Updated on Mar 4, 2011

Inferential Statistics

Inferential statistics are used to interpret data and draw conclusions. They tell psychologists whether or not they can generalize from the chosen sample to the whole population, if the sample actually represents the population. Inferential statistics use rules to evaluate the probability that a correlation or a difference between groups reflects a real relationship and not just the operation of chance factors on the particular sample that was chosen for study. Statistical significance (p) is a measure of the likelihood that the difference between groups results from a real difference between the two groups rather than from chance alone. Results are likely to be statistically significant when there is a large difference between the means of the two frequency distributions, when their standard deviations (SD) are small, and when the samples are large. Some psychologists consider that results are significantly different only if the results have less than a 1 in 20 probability of being caused by chance (p = .05). Others consider that results are significantly different only if the results have less than a 1 in 100 probability of being caused by chance (p < .01). The lower the p value, the less likely the results were due to chance. Results of research that are statistically significant may be practically important or trivial. Statistical significance does not imply that findings are really important. Meta-analysis provides a way of statistically combining the results of individual research studies to reach an overall conclusion. Scientific conclusions are always tentative and open to change should better data come along. Good psychological research gives us an opportunity to learn the truth.

Elementary Statistics

Practice questions for this study guide can be found at:

Research Methods Review Questions for AP Psychology

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