## Statistics 2.4, 2.5, 3.2

##### Created by:

ambition215  on September 17, 2011

##### Description:

statistical graphs, what are bad graphs and why, and characteristics of the center

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# Statistics 2.4, 2.5, 3.2

 frequency polygonuses line segments connected to points located directly above class midpoint values
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#### Definitions

frequency polygon uses line segments connected to points located directly above class midpoint values
relative frequency polygon variation of the basic frequency polygon. uses relative frequencies (proportions or percentages) for vertical scale. to compare two data sets, graph to relative frequency polygons on same axes
Ogive useful for determining the number of values below some particular value. it's a line graph that depicts cumulative frequencies. uses class boundaries along the horizontal scale (X) and cumulative frequencies along vertical scale (Y)
dot plot consists of a graph in which each data value is plotted as a point along a scale of values. dots representing equal values are stacked
stem plots represents quantitative data by separating each value into two parts: the stem (the leftmost digit) and the leaf ( the rightmost digit)
pie chart a graph that depicts qualitative data as slices of a circle in which the size of each slice is proportional to the frequency count for the category
nonzero axis some graphs are misleading because on or both of the axes begin at a value other than zero, so differences are exaggerated
pictographs drawings of objects, are often misleading because they can create false impressions that distort differences
measure of center a value at the center or middle of a data set: several way to determine the center; different definitions like mean, median, mode, and mid-range
mean an average; arithmetic mean of a set of data = the measure of center found by adding the data values and dividing the total by the number of data values
sample size (n); the number of data values
mean formula the sum of all data values/ the number of data values
median a data set = the MOC that is the middle value when the original data values are arranged in order of increasing/decreasing magnitude
median rules 1. if data values = odd, then median is in exact middle of list
2. if data values = even, median is found by computing mean of two middle numbers
mode data set = the value that occurs with the greatest frequency
bimodal two data values occur with the same greatest frequency
multimodal when more than two data values occur with same greatest frequency; each one is a mode
no mode when no data value is repeated
midrange data set = the MOC that is the value midway between maximum and minimum values in the original data set; found by adding maximum data value to minimum data value / 2
midrange formula maximum data value + minimum data value / 2
round-off rule carry one more decimal place than is present in original set of values;

because values of the mode are the same as some of the original data values, they can be left as is without any rounding

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