Data Sampling

Debra Dortch                   Henry Suder Elementary
                               2022 West Washington
                               Chicago, IL  60602
                               (312)534-7864      

Objectives: 

Students will be introduced to data sampling.
Students will turn the data collected into useful information, make graphs
  and use the graphs to solve problems.

Materials needed:

600 mL of soil for each group
uncooked twist macaroni (worms)
dried lima beans (seeds)
small rocks
large sealable plastic bags
measuring cups
newspaper
rulers
balance scales

Strategy:

Divide the class into four groups.  Give each group, except one, a soil mixture 
of 600 mL of soil, 15 lima beans, 150 mL of rocks and 75 mL twist macaroni.  
The other group will get the same soil mixture, except use 150 mL twist macaroni 
instead of 75 mL macaroni.  Label each bag with a different letter 
corresponding to a different spot on a backyard map you have drawn on the board 
or overhead projector.  Do not tell which group has the bag with the most worms. 

Tell the class this story;  

You love to fish and decide that you would like to take a few friends on a 
fishing trip on Saturday.  You will need a lot of worms (at least 50).  You will 
need to dig many holes in the backyard to find that many worms.  Your mother 
would rather you not dig so many holes in her yard.  You remember in science 
class that you learned about sampling.  You ask if you can dig just four holes 
and from these four holes you will examine the dirt and replace the soil.  By 
taking these four samples you can pick the best spot for worms.  Then you will 
need one large hole in that spot and you promise to fill it in again.  Your 
mother loves the idea and, thanks to science, your fishing trip is saved.       

Pass out newspaper, bags of soil, measuring cups and maps of the backyard.  Have 
balance scales and rulers on a nearby table so the students can use these as 
part of the observations.  Share these predictions with the class by writing the 
results of the findings on the chalkboard.  Predict at this time which soil 
mixture will have the most worms. 

The students will complete a table and organize their data.  Pass out a data 
table with columns marked "number of worms", "number of rocks" and "number of 
seeds."  Label the rows of the table with the soil amount (75, 150, 300, 450
and 600 mL).  Count only the contents of the 75, 300 and 600 mL sample and 
predict the contents of the remaining two.  Each child must replace each soil 
sample completely into the bag before taking the next measurement.  At no time 
should the entire contents of the bag be dumped onto the newspaper.  Only the 
measured amount needs to be poured out for counting.  

Conclusion:

Using the measured data, have students complete the table and predict the 
missing data.  Discuss these predictions and record them on the chalkboard or 
the overhead projector.  Draw three graphs using the soil measurements (x-axis), 
and the observed number of seeds, worms and rocks (y-axis).  One student from 
each group will graph his groups counting for each graph.  Compare the graphs 
with the tables.  The class can decide which soil mixture is worm rich by using 
the graphs and the tables. 

Evaluation:

Post activity discussion can focus on some of these questions:

1) Which method of prediction was easier, using the tables or graphs?
2) Can you name four ways in which we observed the soil?
3) Can you name other ways in which data collection can be used in real life?

References:

Reeling in Data Samples, Janis Lange and Stephanie Williamson 
                            March 1990  Science and Children