BACKGROUND:
When scientists tell
others about their work, they frequently display their data using charts
and graphs. Graphs and charts can be easily read and interpreted.
This makes them an effective means of communication. Graphs and charts
have been used since written record was developed, and graphing techniques
are still used today. There are even computer graphing programs that
help scientists, economists, statisticians, and many other people interpret
data easily.
In this lab, students make a
bar graph to record estimated quantities of items and then compare the
actual amounts. Place different items in different containers or
beakers. If using the module, store the materials in the plastic
bags. Items can be marbles, beans, beads, or other objects.
PROCEDURE:
 Review
how to make an "educated guess." Next, have students estimate how
many items they think are in only one of the containers. Record the
prediction. Then have them count the items and record the information.
Do one container at a time. After students complete this first part,
make a bar graph of their findings. See the example below to help
guide your students.
 The margin of error
reflects the difference between the actual answer and the projected answer.
Discuss how to determine the margin of error. Now have students predict
and count the other containers. See if the students' margin of error
is reduced. If so, students are learning that with practice they
can estimate with a smaller margin of error.
