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11 Cards in this Set
- Front
- Back
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What is a density Curve?
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Represents the proportion of the observations, the total area under the curve is equal to 1.
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If a set of observations is symmetric, what can you say about the mean and median?
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They are equal
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What is a frequency histogram?
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A frequency histogram plots the frequency (counts) of each outcome
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68-95-99.7 Rule
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If a set of data is normally distributed then...
68% of observations fall within 1 standard deviation 95% of observations fall within 2 standard deviations 99.7% of distributions fall within 3 Standard deviations |
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How do you standardize data?
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z = (xbar - mu)/st. dev.
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To calculate the percentile you would do the following...
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state the problem
standardize the data (calculate z) draw a picture (using the standard normal curve) Use the table A to find percent. |
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When would you measure the center with median? When would you measure the center with mean?
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The measure of center can be determined by the mean when the distribution is symmetric, and median should be used when the distribution is skewed. (use 5-number summary)
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Describe a normal distribution
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All normal distributions have the same overall shape (symmetric) and are described by the standard normal curve with notation
N(μ,σ) |
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What would it mean if the σ is very large?
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this means the standard deviation is large and the curve is smore spread out.
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What is the inflection point on the standard normal curve and what does it mark?
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It is the points on the curve where the direction changes, and marks the standard deviations. (draw picture)
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If an observation has a z score of 1.98, what does this imply?
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It is 1.98 standard deviations above the mean. We can find the percentile by using the standard normal curve table A.
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