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Chapter 2
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Gravity
Terms in this set (17)
Percentile
the value in a data set with p percent of values lower than it. alculated by dividing the number of values less than p divided by the total number of values.
Frequency Graph
A graph showing the counts (or frequency) of each class in a distribution.
Relative Frequency Graph
A graph showing the percent values of each class from the whole.
Cumulative Relative Frequency Graph
The cumulative relative frequency of successive class is the relative frequency of that class added to the ones below it. Graphed by plotting a point corresponding to each class at the smallest value of the next class.
Z-Score
Also known as the standardized score. Tells how many standard deviations from the mean an observation is, and in what direction.
Calculated using the following formula:
(X - Mean) / Standard Deviation
Adding/Subtracting a Constant
Affects measures of center, but not shape or spread
Multiply/Dividing a Constant
Affects measures of center and spread, but not shape
Density Curve
Describes the overall pattern of a distribution. The area under this curve and within any interval on the axis is the proportion of all data values falling into that interval.
Always:
1. on or above the horizontal axis
2. area of 1 under the curve.
Median of Density Curve
The equal-areas point of a density curve, at which area is equal on either side.
Mean of Density Curve
The balancing point of a density curve, where the curve would balance if made of solid material.
Normal Distribution
A distribution that is described by a normal density curve, and is completely specified by its mean, μ (mu), and its standard deviation σ (sigma). Abbreviated by N(μ, σ).
Normal Curve
A symmetric, single-peaked, and bell-shaped curve, that describes a normal distribution. The mean μ is located at the center of the curve, and the standard deviation σ is the distance from the center to the inflection points on either side.
68-95-99.7 Rule
the Empirical Rule: 68% of the observations are within one standard deviation from the mean, 95% within two, and 99.7% within three standard deviations on either side of the mean.
Standard Normal Distribution
A normal distribution with a mean of 0 and a standard deviation of 1.
Standard Normal Table
Also known as Table A, this is a table of the areas underneath a standard normal curve. It gives the area to the left of a specific z-value.
normalcdf(
Command used on a TI84 calculator to find the area to the left of a specific z-score on a normal curve
invNorm(
Command used on a TI84 calculator to find the value corresponding to a given area to the left of that value
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