Theme: Honing Math
Skills in the Garden
Grappling with Data
Making Sense of Investigations
Whether your young scientists are conducting indoor plant experiments
("What conditions promote the best bean plant growth?") or outdoor
habitat research ("Which plants do different types of butterflies
prefer?"), they'll need to practice accurately gathering and
organizing their data. By learning how to represent their data
so patterns are revealed, students will be able to make better
sense of their experiences. This article describes some plant-related
challenges, and suggests strategies to help your students think
and act like scientists as they grapple with data from their
indoor and outdoor gardening experiences.
Data Gathering Challenges
What students choose to observe and measure will depend, in
part, on the nature of their question, experimental setup, hypotheses,
and so on.
Clarifying Terms
To help students decide what types of information to gather,
you might first have to help them clarify the language in their
question or hypothesis. For instance, with plant-related investigations,
students often want to know which treatment will result in the
"best" plant growth. Challenge them to define what they mean
by "best" and imagine what type of data would support their
predictions or hypotheses: the tallest plant? The greenest?
The one with the most leaves? Once they've answered these questions,
they can better clarify what they'll observe and measure. (Consider
starting by brainstorming a list of the factors that students
might look at: height, number of leaves, color of leaves, number
of branches, root length and shape, stem width, leaf area, distance
between nodes, and so on, then choose some that students believe
may be the best indicators of plant health. Setting
Standards
A similar challenge with classroom data gathering is the need
for "standards" of measurement. This is particularly important
if you have a number of students or groups working on different
aspects of one investigation. "We had several classes working
together on an investigation of light tubes," says fourth grade
Chicago, IL, teacher Paul Scott. "When students first started
posting data, some noticed that there was no uniformity in the
way people were taking plant height measurements. Some were
measuring from the soil to the end of the longest branch, while
others measured from the lowest branch to the end of the top
leaf. Students quickly realized that we needed to establish
a standard." You might choose to establish (and practice) measurement
standards up front, or let students discover the need themselves
(with your questions and guidance) as they conduct and review
their investigations.
While some data are obviously quantifiable, such as measurements
of height, length, mass, volume, or responses to a survey, other
observations may be more qualitative, based on sensory descriptions
of objects and phenomena (e.g., how worms respond to light).
Older students may be able to create more subjective comparisons
by quantifying descriptive information. If students were comparing
leaf colors, for instance, they might use magic markers to identify
different shades, then assign a score to each of the three or
four shades, and compare average scores between plants in the
treatment and control groups.
Cultivating Keen Observers
Observation is one of those skills teachers assume students
have. But without guidance, student observations often lack
detail and precision. Giving students adequate time to observe
carefully, providing tools (e.g., hand lenses) to enhance observations,
and encouraging detailed descriptions with precise language
and drawings can improve students? observations and encourage
them to think and act like scientists.
Honing in on Data
"When my sixth graders set up plant experiments," reports LaCrescent,
MN, teacher Scott Tyink, "they often chose to look at only one
factor--plant height, for instance--but later they began to
notice other factors like the leaf color, shape, or flowers.
It can be a challenge to persevere and sift through data. Sometimes
students realized in the midst of experiments that they hadn't
collected enough data or collected it well enough to make sense
of it. This helped them understand the need to plan and sometimes
revise investigations."
Organizing It
By structuring how students record their observations, you can
help them recognize the importance of organizing the information
they gather. GrowLab forms that help students record their investigation
observations and data include "My Plant Journal" for younger
students and the "Observation Journal" for older students. Both
are located in GrowLab: Activities for Growing Minds.
A science journal or notebook is another tool for documenting
investigations. One technique for structuring entries is to
have students divide each journal page, with one half for observations,
drawings, and measurement, and the other half for thoughts and
questions prompted by their observations.
To get students in the habit of systematically recording experimental
data as scientists do, consider using data tables. A data table
is typically a titled chart that includes the manipulated or
independent variable (e.g., soil type) in the lefthand
column and the responding or dependent variable (e.g., time
it takes to drain a cup of water) in the next column. If students
repeat the trial for each variable or collect data from a number
of groups, they can include a third column to record an average
(e.g., average drainage time. The information from a data table
can later be transferred to a graph so patterns are more easily
revealed.
Representing It
To be able to make sense of information gathered during a plant
investigation -- compare results, find patterns, and make explanations
-- it helps to have a visual overview of the information. There
are many ways to organize data from an investigation including
"before and after" drawings, concept maps, classification schemes,
oral descriptions, and models. Older students can create more
sophisticated organizers and review data taken over time and/or
from multiple experiments. Here we will focus on different types
of charts or graphs.
Have students consider what information they are trying to
depict. By exposing students to different types of charts or
graphs, helping them understand when it's most appropriate to
use each one, and modeling how to create each type, you will
prepare them for making appropriate choices as classroom scientists.
HISTOGRAM - Students should use this type of bar graph
when they want to represent frequencies -- for instance, the
number of students surveyed who have x as a favorite vegetable.
PIE CHARTS - These are used to depict parts of a whole --
the fraction of the garden that is devoted to herbs, vegetables,
annuals, and perennials, for example.
BAR GRAPHS - These should be used to show comparisons of
data with discreet categories such as days to germination for
different types of vegetable seeds.
LINE GRAPHS - Upper elementary students might use these
to show correlation among variables when the intervals on each
axis are equal and continuous (e.g., height, time, temperature,
volume). For instance, students could use a line graph to depict
how incremental amounts of fertilizer affect plant height. They
would choose a bar graph to depict how different soil types
affect the size of leaves plants produce.
Because plants (ideally) grow continuously, many of your students'
experiments will involve tracking change in plant growth over
time. In these cases, students might construct a line graph
with the dependent variable (e.g., height) on the y axis, time
on the x axis, and plot a set of points for each independent
variable (for example plants grown in soil, sand, and clay).
More Graphing Tips
All charts should be titled, and graphs should include the manipulated
variable (independent) on the x the responding variable (dependent)
on the y axis, and feature labels and units for each. Students
should be able to plot points from their data tables on line
graphs, then draw a "line of best fit" between or near data
points that offers a visual image of the correlation between
variables. Students should be able to write a sentence or two
that summarizes the data (e.g., As the amount of fertilizer
increased, the intensity of green leaf color increased).
Teachers often find that student-designed graphs make poor
use of space. One method for helping students choose appropriate
intervals for measurements on an axis is to have them first
find the difference between the smallest and largest values
for a variable, such as height. (They can use these values for
the bottom and top of the axis.) If they divide the difference
by five (an arbitrary number that seems to work well) and round
to the nearest whole number, they'll get a number that they
can use for the intervals on that axis.
Measuring Mania
"With a goal of honing my fourth graders' metric skills and
encouraging them to think about fair tests, I set up a contest
to see which small group could grow the 'biggest' lima bean
plant, "reports Nashville, TN, teacher Nancy Johnson. To decide
how to determine the "biggest" plant, students first used rulers
to measure heights of standard objects to improve measurement
skills, then measured the heights of their group's plants. "Students
wanted to measure the heights of the other groups' plants too,"
says Nancy, "to be sure that the 'competition' was also measuring
correctly!" To reduce individual competition and increase cooperation,
students decided to total the sizes of each group member's largest
plant. Each child made an individual data table for his or her
journal, and the class made a group data table to track the
whole contest.
Author: Eve Pranis
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