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Chapter 8: Statistics: An Introduction
8.1 Statistical Graphs
8.1.1. Vocabulary
8.1.1.1. data – a collection of information on a topic
8.1.1.2. pictograph –a symbol or icon is used to represent a quantity of
items
8.1.1.3. line plot – marks placed above a number line representing each
item of data collected
8.1.1.4. outlier – a data point whose value is significantly larger or smaller
than the other data values present
8.1.1.5. cluster – isolated group of points
8.1.1.6. gap – a large space between points
8.1.1.7. stem-and-leaf plot – closely related to a line plot, but the number
line is usually vertical and digits are used instead of marks
8.1.1.8. stems – numbers on the left side of the vertical line
8.1.1.9. leaves – numbers on the right side of the vertical line
8.1.1.10. ordered stem-and-leaf plot – all of the digits are in order
8.1.1.11. double stem-and-leaf plot – two data sets on either side of a single
number line
8.1.1.12. classes – intervals of scores
8.1.1.13. grouped frequency table – shows how many times data points
appear in each class
8.1.1.14. histogram – graph created from grouped frequency table – bars
touch
8.1.1.15. bar graph – graph created from nominal or ordinal data – bars do
NOT touch
8.1.1.16. line graph – vertical and horizontal number lines – connects tops of
bar graphs – use solid line for continuous data; use dotted line for
discrete data
8.1.1.17. scatter plot – used to determine a relationship between two types of
data
8.1.1.18. trend line – best fit line through a scatter plot – divides points in half
8.1.1.19. correlation – the relationship between two types of data
8.1.1.20. circle graph – circular region partitioned into disjoint regions
8.1.1.21. pie chart – another name for circle graph
8.1.2. Pictographs
8.1.2.1. Often used by
8.1.2.1.1. children
8.1.2.1.2. magazines
8.1.2.1.3. newspapers
8.1.2.2. symbol or icon represents quantity of items
8.1.2.3. frequently used for comparisons of outputs
8.1.3. Dot Plots/Line Plots
8.1.3.1. no numerical values are lost in the graph
8.1.3.2. quick, simple way of organizing numerical data
8.1.3.3. outlier
8.1.3.3.1. data point that does not “fit” in with the rest of the data
8.1.3.3.2. significantly larger than other data points
8.1.3.3.3. significantly smaller than other data points
8.1.3.4. cluster - isolated group of points
8.1.3.5. gap – large space between points
8.1.4. Stem-and-Leaf Plots
8.1.4.1. closely related to line plot
8.1.4.2. number line usually vertical
8.1.4.3. digits used to represent data points
8.1.4.4. see figure 8-5, 8-6, 8-7 p. 507-509
8.1.4.5. key MUST accompany all plots
8.1.4.6. graph should be titled
8.1.4.7. Now try this 8-1 p. 508: Discuss in your groups
8.1.4.8. How to construct a stem and leaf plot:
1. find the high and low values of the data
2. decide on the stems
3. list the stems in a column from least to greatest
4. use each piece of data to create leaves to the right of the stems on the
appropriate rows
5. if the plot is to be ordered, list the leaves in order from least to greatest
6. add a legend or KEY identifying the values represented by the stems
and leaves
7. add a title explaining what the graph is about
8.1.5. Back to Back Stem and Leaf Plots
8.1.5.1. double stem and leaf plots are used to readily compare two sets of
data
8.1.5.2. Now try this 8-2 p. 509: Discuss in your groups
8.1.6. Frequency tables
8.1.6.1. frequency table can be formed by listing all possible data points for
the range of data as in a line plot and then tallying the frequency of data
points occurring at each point
8.1.6.2. classes are formed from grouping equal ranges of data points
8.1.6.3. frequency table can be formed by listing classes and tallying the
number of data points occurring in each class
8.1.7. Histograms and Bar Charts
8.1.7.1. histogram is a graph constructed from a frequency table consisting
of classes
8.1.7.1.1. classes must be equal
8.1.7.1.2. bars touch
8.1.7.2. bar graph is constructed from frequency table for single data points
8.1.7.2.1. data can be
8.1.7.2.1.1.
nominal
8.1.7.2.1.2.
ordinal
8.1.7.2.1.3.
interval/ratio
8.1.7.2.2. bars do NOT touch
8.1.7.2.3. See all figures p 510, 512
8.1.8. Line graphs
8.1.8.1. shows relationships between data
8.1.8.1.1. calculator will plot for you 
8.1.8.2. two axes used
8.1.8.3. sometimes used for time graphs – time is horizontal axis
8.1.8.4. Discrete data is plotted with dotted line
8.1.8.5. Continuous data is plotted with a solid line
8.1.8.5.1. See figure p. 513
8.1.9. Scatter plots
8.1.9.1. shows relationship between data – if one exists
8.1.9.1.1. calculator will calculate for you 
8.1.9.2. trend line divides data in half – LSR (least squares regression line)
8.1.9.2.1. calculator will calculate for you 
8.1.9.3. Correlations
8.1.9.3.1. positive
8.1.9.3.2. negative
8.1.9.3.3. none
8.1.9.4. See all figures p. 513
8.1.10. Circle Graphs (Pie Charts)
8.1.10.1. ALWAYS represent 100% of the data
8.1.10.2. shows how parts are related to the whole
8.1.10.3. See all figures p. 514-515
8.1.11. Choosing a data display
8.1.11.1. Now try this 8-3 p. 516: Discuss in your groups
8.1.12. Ongoing Assessment p. 517
8.1.12.1. Home work: 2ac, 3, 4, 5a, 7ac, 8, 10a, 11ac, 12a, 16a, 18a, 19,
20a, 21bc, 22ac, 23ac, 25ace