Raw data
Have not been manipulated or treated in any way beyond their original collection
Frequency distribution
A table that divides the data values into classes and shows the number of observed values that fall into each class
histogram
Describes a frequency distribution by using a series of adjacent rectangles, each of which has a length that is proportional to the frequency of the observationswithin the range of values it represents.
Class
Each category of the frequency distribution
Frequency
The number of data values falling within each class
Class limits
The boundaries for each class. These determine which data values are assigned to that class
Class interval
The width of each class. This is the difference between the lower limit of the class and the lower limit of the next higher class.
Approximate class width
(Largest raw date - smallest raw data)/ # of classes desired
Class mark
The midpoint of each class. This is midway between the upper and lower class limits
Guidelines for frequency distribution
-classes must be mutually exclusive -exhaustive-equal widths -right # of classes-class widths = round #s-no open-end classes
Relative frequency distribution
the proportion or percentage of data values that fall within each category
Cumulative frequency distribution
List the number of observations that are within or below each of the classes.
Frequency polygon
consists of line segments connecting the points formed by the intersections of the class marks with the classfrequencies
Ogive
a graphical display providing cumulative values for frequencies, relative frequencies, or percentages.
Stem-and-leaf display
a variant of the frequency distribution, uses a subsetof the original digits as class descriptors
Dotplot
displays each data value as a dot and allows us to readily see the shape of the distribution as well as the high and low values
Bar chart
-Represents frequencies according to the relativelengths of a set of rectangles, but it differs in two respects from the histogram:(1) the histogram is used in representing quantitative data, while this represents qualitative data; and (2) adjacent rectangles in the histogram share acommon side, while these have a gap between them
Line graph
capable of simultaneously showing values of two quantitative variables (y, or vertical axis, and x, or horizontal axis); it consists of linear segments connecting points observed or measured for each variable
Pie chart
a circular display divided into sections based on either the number of observations within or the relative values of the segments
Pictogram
Using symbols instead of a bar, it can describe frequencies or other values of interest.
Sketch
Varies in size depending on the frequency or other numerical value displayedA drawing or pictorial representation of some symbol relevant to the data
Scatterplot
Each point in the diagram represents a pair of known or observed values of two variables, generally referred to as y and x, with y represented along the vertical axis and x represented along the horizontal axis
Direct relationship
Both x and y increase together
Inverse relationship
Y decreases as X increases
Curvilinear relationship
The best fit line is a curve
No relationship
The best fit line is horizontal, with a slope of zero
Tabulation
Simply count how many people or items are in each category or combination of categories.
Simple tabulation
-AKA marginal or one-way-count how many people or items are in each category
cross-tabulation
-AKA contingency table or two-way crosstab-Shows how many people or items are in combinations of categories