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(Ch. 13) GRE Statistics Review
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Terms in this set (14)
Median
the middle score in a distribution; half the scores are above it and half are below it
Mode
The term that appears most frequently in a set
Range
The distance between the greatest and and least values in a group of data points
Interquartile Range
Q₃ - Q₁
boxplot (box and whisker plot)
A visual representation of quartiles that uses 5 values:
L = least number in the data
G = the greatest number in the data
M = median
Q₃
Q₁
A Number line is drawn underneath it to represent the values
Percentiles
Used for large groups of numbers, but the same concept as quartiles, with 100 subdivisions instead of 4.
Q₁ = 25th percentile
Q₂ = 50th percentile
Q₃ = 75th percentile
Q₄ = 100th percentile
Quartiles
When a data set is arranged in chronological order and subdivided into 4 sets of terms (the quartiles).
Q₁ = largest number in first/lowest group
Q₂ = largest number in 2nd group
Q₃ = largest number in 3rd group
Q₄ = largest number in data set (aka highest group)
Standard Deviation
an estimate of the average variability (spread) of a set of data measured in the same units of measurement as the original data. It is the square root of the variance.
Frequency distribution
a description of how often certain data values occur in a set and is typically shown in a table or histogram. May show in percentage or count.
Relative frequency distribution
A distribution of fractions (or decimals) describing the number of occurrences of each value of a variable.
normal distribution curve (bell curve)
special kind of frequency distribution that is closely tied to the concept of standard deviation, used with many natural data sets. Only two parameters are needed to define it: the mean and the SD. The mean = median in a normal distribution curve
Histogram
Bar graphs that show relative frequencies (numbers of occurrences). Y-axis shows the frequency, the x-axis is a category of definitions, values, ranges, etc.
Segmented bar graph
Used to compare the distribution of a categorical variable in each of several groups; for each value of the categorical variable, there is a single bar with "segments" that correspond to the different values of the categorical variable; the height of each segment is determined by the percent of individuals in the group with that value; each bar has a total height of 100%
Formula of a slope
(y₂ - y₁) / (x₂ - x₁)
;