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14 Cards in this Set
- Front
- Back
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How do we modify the population variance formula to get the formula for estimated population variance?
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Divide by N-1 instead of N.
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Why do we need to calculate S-squared instead of using SD-squared when estimating population variance?
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The SD-squared formula underestimates the true population variance. S-squared corrects this by giving us a slightly larger result.
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When do we use a t-test?
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When population variance is unknown.
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What are degrees of freedom (df)?
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The number of cases that can take on any score while giving you a particular parameter value.
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How do we calculate degrees of freedom (df)?
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N-1 (Number of cases minus one)
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When do you use a single-sample t-test?
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Comparing a sample to a fixed value or a known population mean.
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How do we determine the shape of the comparison distribution for a t-test?
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The comparison distribution is always a t-distribution with a specific shape determined by degrees of freedom.
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What is a within-subjects design?
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A research design that involves comparing cases at two points in time (usually before and after some intervention).
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How do you calculate difference scores?
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Posttest - pretest (or after - before)
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When do we use a dependent-means t-test?
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When trying to determine whether change within a population over time is statistically significant.
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The information constituting the data we actually analyze in a dependent means t-test.
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Difference scores.
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How do you calculate degrees of freedom (df) when conducting a dependent-means t-test?
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Number of cases minus one (N-1)
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In a dependent-means t-test, what is the value for the mean of the distribution of means (Mm)?
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Zero
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In a single-sample t-test, what is the value of the mean of the distribution of means (Mm)?
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Mm will be the same as the population mean (which must be given in the problem).
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