Section 1: Scientific Method
Fundamental Topics in Science © 2001 Texas Instruments Teacher Notes 1-8
Activity—Variations in Human Heart Rate
In this section, students write a statement corresponding to each of the five steps in the
scientific investigation process outlined in
CONCEPTS
. Accurate and effective communication in
written form is an integral part of scientific investigation. It is important that students learn that
proper scientific investigations require discipline in the descriptions and testing. In other words,
it is not appropriate to “wing it,” “make it up as you go along,” or “change horses in midstream,”
to borrow a few clichés. This activity reinforces these ideas.
At any time students can select
Ã
MENU
Ä
to return to the
ACTIVITIES
menu.
Observe.
Students are already aware that heart rates vary from one person to another. In the
activity, they learn about scientific method by investigating this phenomenon. In a
WRITE IT
DOWN
screen, students are asked to list factors they think might affect heart rate.
Hypothesize.
Students begin by investigating a single factor: gender. One of many possible
hypotheses is shown in the application. You may wish to suggest that students try formulating
their own hypotheses in writing. Point out that it is more important that they form a simple,
testable hypothesis than that their hypothesis be correct (i.e., it isn’t improper to formulate and
test a hypothesis that you hope to prove false). Three such hypotheses are:
•
Boys have higher (faster) heart rates than girls.
•
Girls have higher (faster) heart rates than boys.
•
There is no significant difference in heart rate due to gender.
In a
WRITE IT DOWN
screen, students are asked how they could test the hypothesis “males have
higher heart rates than females.”
Test.
As with any open-ended scientific investigation, responses will vary. At this stage, it is not
important that students resolve the question about variation of heart rate among humans. It is
more important that the students explore the steps in the scientific process. Emphasize that a
study of this particular example, like that of other phenomena, can elicit an almost limitless
number of different hypotheses. Each could be investigated using a scientific process.
Tell the students that pulse rate is indicative of heart rate. Show them various ways they might
measure pulse rates. One common method is to place an index finger on a prominent artery,
such as the one found on the underside of the wrist or in the neck just behind the jaw bone.
Tell them it is common to count the number of pulses in a brief period then multiply by a factor.
For example, count the pulses for 10 seconds and then multiply by 6 to estimate the pulse rate as
typically expressed in beats per minute. While convenient, this method introduces error—which
is a great topic for further discussion.
Before beginning the test step, discuss with students what they think might be a reasonable
sample size for testing their hypothesis. The activity suggests they should measure the pulse
rates of at least six classmates.
As students take each other’s heart rates, they enter them on
the activity screen, using
Ã
M/F
Ä
to toggle gender and
Ã
+
Ä
or
Ã
1
1
Ä
to change the measured pulse, and then
Ã
ADD
Ä
. After a person
is added, students can select
Ã
MORE
Ä
to record another sample
or
Ã
MENU
Ä
if they are finished. The cumulative results are
displayed until a key is pressed. Instruct the students if you
want them to record the readings and cumulative result.
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