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Chapter 13

# chapter 13 review

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University of Toronto Scarborough

Psychology

PSYB01H3

Connie Boudens

Fall

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Chapter 13 Understand Research Results: Statistical Inference Infer whether the results that were obtained in a particular study would still occur if the study were repeated over and over again SAMPLES AND POPULATIONS Researchers conduct studies from a single sample of research participants They rarely conduct studies from entire populations; their findings are based ons ample data So with this sample data, you want to be able to make statements about the entire populations and so, you want ot know if the results will be the same if the experiment were conducted again with a new sample Inferential statistics: used to determine whether we can, in fact, make statements that the results reflect what would happen if we were to conduct the experiment again and again with multiple samples Asking if whether we can infer that the difference in the sample means reflects a true difference in the population means Inferential statistics allow us to arrive at such conclusions on the basis of sample data INFERENTIAL STATISTICS Importance of ensuring that the groups are equivalent in every way except the independent variable manipulation Equivalence of groups are maintained by controlling all other variables or by randomization If the groups are equivalent, then you assume that any differences found in the dependent variable are due to the effect of the independent variable Differences between any two groups will amost never be zero o This means that there will be some difference in the sample means, even if you manage to carry out the experiment properly www.notesolution.com o This happens because you are dealing with samples and not populations o Random or chance error will be responsible for some difference in the means even if the independent variable had no effect on the dependent variable o Point is, the difference in the sample means reflects any true difference in the population means plus any random error Inferential statistics allow researchers to make inferences about that true difference in the population on the basis of the sample data Inferential statistics give the probability that the difference between means reflects random error rather than a real difference NULL AND RESEARCH HYPOTHESES Statistical inference begins with a statement of the null hypothesis and a research (or alternative) hypothesis Null hypothesis: the population means are equal the observied difference is due to random error o States that the independent variable had no effect Research hypothesis: the populations means are, in fact, not equal o States that the independent variable did have an effect If we can determine that the null hypothesis is incorrect, then we accept the research hypothesis as correct Acceptance of the research hypothesis means that the independent variable had an effect on the dependent variable With the null hypothesis, we know precisely the probability of the outcome of the study occurring if the null hypothesis is correct So we want to infer that the research hypothesis is correct only by rejective the null hypothesis www.notesolution.com

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