Stats 126 Ch 2 (2.3+2.4)

class midpoint

the sum of consecutive lower class limits divided by 2

frequency polygon

graph that uses points, connected by the line segments, to represent the frequencies for the classes. (class midpoints is x-axis)

cumulative frequency distribution

displays the aggregate frequency of the category. for discrete data, it displays the total number of observations less than or equal to the category. for continuous data, it displays the total number of observations less than or equal to the upper class limit of a class.

cumulative relative frequency distribution

displays that proportion (or percentage) of observations less than or equal to the category for discrete data and the proportion (or percentage) of observations less than or equal to the upper class limit for continuous data.

Ogive

a graph that represents the cumulative frequency or cumulative relative frequency for the class. (x-coordinate is upper class limits)

time series data

if the value of a variable is measured at different points in time.

time series plot

obtained by plotting the time in which a variable is measured on the horizontal axis and the corresponding value of the variable on the vertical axis.

pictograms

rely on graphic representing a certain quantity.

guidelines for constructing good graphics

1. title and label axes clearly

2. avoid distortion. never lie about data

3. minimize amount of white space in graph.

4. avoid clutter

5. avoid three dimensions

6. do not use more than one design in the same graphic

7. don’t try to force a reader to any specific part of graph

8. avoid relative graphs that are devoid of data or scales

9. always start at zero, unless you specifically state that u didn’t want to.