Pre Algebra ( period 1)

Box & Whiskers 12-2


Statistics Unit
(We have covered: 
Mean, Median & Mode: Chapter 3-3

Frequency Tables and Line Plots: Chapter 12-1

Stem and Leaf Plots: p. 618-619)

Box & Whiskers
Uses 3 medians:
(1)the true median,
(2)the median of the upper data and
(3)the median of the lower data

The median divides the data into 2 parts:

The upper data half The lower data half

Now we will take the median of each of these halves.

The data is now separated into 4 quarters which are called QUARTILES
The median of the lower half is called the LOWER QUARTILE
The median of the upper half is called the UPPER QUARTILE
The lower median and the upper median will form the left side and right side of the BOX

The true median will be somewhere inside the box
The lowest value forms the lower WHISKER and the highest value forms the higher WHISKER

These are called the lower extreme and upper extreme
The box represents the MIDDLE 1/2 (50%) of the data


Circle Graphs
Page 471
Find the percent of the total data using the intervals from the histogram

Draw a circle and approximate the percentages of the total circle

Show you how to do it exactly with a protractor and 360 degrees
set up a proportion !!
 
SOMETHING A LITTLE DIFFERENT...
Trend Over Time & Line Graphs
LINE GRAPHS: p. 98-99

Data that takes place OVER TIME is represented well on a Line Graph.

For example, a student's math grade over the course of a year, or over middle school, or even over a single month.
The length of the time interval depends on what you're trying to show.

If you have more than one set of data over the same time period,
you can make MULTIPLE LINES on the graph.

For example, a student's math grade, along with his science grade.


BAR GRAPHS:
 Data over time can also be shown as a Bar Graph, but Bar Graphs are especially useful to show data that compares either non-numeric data or comparing multiple types of the same data at the same time.

Non-numeric data: Really a Line Plot but without the "X's"
Allows you to represent very large data sets easily because you can label the y axis (vertical axis) in any way that you need to.

Numeric data: Going back to a student's grades on the Line Graph...Say you wanted to compare multiple students' math grades and science grades in 8th grade, you could make a DOUBLE BAR GRAPH with one bar color representing math grades and another bar color representing their science grades