HOW WHEN AFFECTS WHAT
Part 1: When You Look, Where you Look
* From Aspen Global Change Institute 1992 - Ground Truth Studies
Students will gather and record visual and written data from their surroundings, and show how the time of data
collection, or the sampling window, can affect an outcome, sometimes resulting in false conclusion.
In global change research, as in any scientific research, the timing and duration of data collection, and the
window of the data set are of critical importance in reaching accurate conclusions This is best illustrated by
seeing how “truth” can easily be distorted by isolating a part of the complete data set or by collecting data at a
particular time. Issues such as natural variability often come into play, and it is important to evaluate cause and
effect, effect and cause.
In this activity, students will photograph and/or count the number of people in the public areas of the school such
as the cafeteria or gym. They will also consider various “windows” of time within which to examine data. They
will discuss what conclusions might be drawn from their data seta and why these conclusions might not be
accurate. In part two of this exercise, students will then examine global change data, a graph of global tempera-tures,
and extend their understanding of how time of data collection and the window of the data set affects
conclusions. It may also be suggested to the students that they measure and compare daily temperatures instead.
- Camera and film (preferably instant developing film or a video camera for instant results)
- graph paper
- pencils & pens
- Have students choose a public area of the school as their subject of study. They should image (count or
photograph the people in) these areas from above (from a window, high up in a nearby building) at various
times of day, say 8 am, and lunchtime, and on different days of the week, and count the students that appear
at each time. They can choose some special times to collect data.
- The students should then graph their data and describe what they have learned about the phenomenon they
measured — such as average number of students counted, based on when the observations were made.
Ask your students to examine their data and pose questions that can be answered by evaluating the data. How
would someone interpret the data if they did not know where and when it had been collected? What kinds of
conclusions can be drawn from the information collected? How did the time of collection affect the answers to
the question posed? How did the window selected affect the outcomes? How might the data be interpreted or
misinterpreted? Students can come up with conclusion they know are false, but which can be supported by their
data sets. Have your students discuss ways in which information might be unintentionally misread or intentionally
- Ask the students to design a sampling schedule which would help avoid gross distortions of reality, but
which do not require continuous sampling.
- Have students bring in examples from articles in the press which demonstrate the effect of how and when
data is collected has an impact on the conclusions drawn.
Last modified prior to September, 2000 by the Windows Team
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