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19 Cards in this Set
- Front
- Back
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Population
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collection of people / entire group interested in
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Census
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data on all the cases out there; every 10 years in USA
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Sample
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subset of cases selected from underlying total population
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Population Distribution
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• Y on x axis
• Center at MY • One standard deviation? |
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Sample Distribution
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a subset of the population which we have data on
• We want to use the sample to say something about the population • Y on x axis • Centered at Y Bar • One standard deviation from mean |
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Sampling Distribution
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a distribution of all the means we could have gotten if we sampled infinitely; the distribution of y bars (means); does NOT exist, just a hypothetical thought experiment; what could have happened if I had gotten a different mean (y bar)
• Centered at MY Bar (equals MY) • Y Bar on x axis • One standard error from Mean |
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Parameter
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Value used to represent certain population characteristic
• Population mean is a parameter used to indicate average value of a quantity |
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Statistic
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Quantity calculated from sample of data
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Standard Error
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standard deviation of sampling distribution – how far off on average we are from the mean
• sigmaY /square root N |
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Null Hypothesis
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comes from someone else; what you are trying to disprove
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Alternative Hypothesis
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What your hunch is; what you are trying to prove
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P-Value
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probability of observing results as supportive of alternative hypothesis or more supportive of what we got if null is true
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Statistical Significance
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when we have a p-value of less than .05; we are able to reject the null
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Type I error
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reject a true null hypothesis; worst b/c we are going against conventional wisdom and we are wrong
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Type II error
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accept false null; go along with conventional wisdom
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Confidence Interval
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likely location of population mean
• Calculated by adding lowest and highest values to original (null) value |
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Normal Distribution
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bell curve distribution; symmetrical around mean, has predictable area under curve, one standard deviation captures 68% area under curve, two standard devs. 95%, and three = 99%
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T-distribution
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Fatter tails than normal distribution
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• T-score
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how many standard errors Ybar is away from MY under the null
• Bigger score, then reject null |
