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40 Cards in this Set
- Front
- Back
statistics
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the art and science of collection, analysing, presenting, and interpreting the data.
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data
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the facts and figures collected. analyzed, and summarized for presentation and interpretation
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elements
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entities of which data is collected. ex. AB stock`
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variables
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charecteristics of interest for the elements. ex. NYSE, OTC
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observations
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measurments of each variable for every element
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qualitative
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names and labels
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quantitative
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numbers, numeric
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existing source for obtaining data
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internet, census, employers, etc.
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experimental study for obtaining data
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test and control
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observational study for obtaining data
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survey, observations
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statistical inferance
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using a sample to generalize about a population
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frequency table
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table showing the number for frequency of items in each of several non overlapping classes
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n=
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sample size
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relative frequency
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proportion of occurance. freq/n. sum of relative frequencies should equal 1
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percent frequency
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percent of occurance. rel. freq x 100
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bar graph
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qualitative data. bars do not touch
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histogram
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quantitative data. bars touch eachother.
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pie chart degrees for a sector=
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rel. freq. x 360
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how many classes in quantitative data?
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5-20
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width of each class in quantitative data?
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high value - low value / # of classes
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∑
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sum.
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-
x |
sample mean. ∑x/n
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µ
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population mean. ∑x/N
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n
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sample size
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N
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population size
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mean
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average
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median
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middle number
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mode
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most frequently occuring number. bimodal, multimodal
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i
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index for percentile. (p/100)n.
if i has a deciamal, bump it up. if i is whole, average of i and i+1. |
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range
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highest # - Lowest #
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interquartile range (IQR)
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Q3-Q1
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variance
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a # that describes how much the data varries from the mean
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2
s |
sample varience.
- 2 ∑(x-x) / n-1 |
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2
σ |
population variance.
2 ∑(x-µ) /N |
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standard deviation
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amount an observation varries from the mean
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s
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sample standard deviation.
2 s=✓s |
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σ
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population Standard Deviation.
2 σ=✓σ |
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z
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z score.
_ x-x/s x minus mean divided by standard deviation |
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chebyshev's therom
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2
at least (1-(1/z )) of the data values must be within z standard deviations of the mean, where z is any value greater than 1. at least 75% within z=2 89% within z=3 94% within z=4 |
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emperical rule
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symetrical distribution of data in the shape of a bell.
68% within 1 sd 95% within 2 sd almost all within 3 sd |