EXERCISE 1 - SCIENTIFIC METHOD
OBJECTIVES
After completing this exercise, you should be able to:
•
•
•
•
•
•
formulate a testable hypothesis
explain what a control is and why it offers validity to experiments
collect and organize data for analysis
calculate the mean, median, mode, and range for a set of data
construct graphs that clearly and accurately represent a set of data points
identify the characteristics of well constructed versus poorly constructed graphs
SUPPLIES
Activity 3
one 30 cm long metric ruler
ACTIVITY 1 - STEPS OF THE SCIENTIFIC METHOD
When scientists approach a question or a problem, they do it in a very simple and structured way. In
general, the process that scientists use in answering questions uses the following steps:
•
•
•
•
•
Observation
Develop Hypothesis
Design Experiment to Test Hypothesis
Collect Data and Analyze Results
Conclusion
Once a conclusion is reached, that's not the final answer. Conclusions are always subject to review and
interpretation as more information is collected about the topic. If the results don't support the original
hypothesis, scientists will usually form a new hypothesis and try again.
You've heard the word hypothesis many times, but what is it? How is a hypothesis developed? A
hypothesis is an educated guess, based on facts. A hypothesis must be based on evidence, even if that
evidence is simply your own prior experience. Therefore, it must be logical.
A good hypothesis has two essential feature: it is specific and it is testable. The more specifically the
hypothesis is stated, the easier it is to develop a method to confirm or reject the hypothesis.
For example, if you misplaced your homework, a bad hypothesis might be "the dog ate it," because this
would be both unlikely and difficult to confirm. A better hypothesis might be "I left it in the computer
lab or I left it in the car," because these are quite simple to test, and are very specific.
Mark all the "bad" or poorly framed hypotheses in the following list. Rewrite each hypothesis that you
marked into an acceptable format.
1.
_____
Spinach makes you stronger.
2.
_____
Adding fertilizer to tomato plants will cause them to produce more fruit.
3.
_____
Susan will lose weight by taking Quick-Loss Diet Pills.
4.
_____
Soft contact lenses are better than hard contact lenses.
ACTIVITY 2 - DETAILS OF AN EXPERIMENTAL SETUP
Once you have developed a hypothesis, you may wish to test your hypothesis with an experiment. In
science, experiments must be designed in a specific way, so that the results will be accurate. One facet
of these procedures is the concept of a control.
I looked into my neighbor's yard and notice that his rose bushes are big and bushy and covered with
flowers. I say to him, "How did your roses grow so big?" He replies that he fertilized the bushes. I
say, "Great. I can do the same to make my bushes as wonderful as yours, but, by the way, how can
you be sure that the fertilizer was the cause of all this growth?" And he says to me, "Gosh I really
don't know for sure. I fertilized them and they grew pretty well this year. I guess that the fertilizer
caused this excellent growth." And I reply, "Are you sure it wasn't because we had more rainfall this
year? Or that the weather wasn't as hot as usual?" So, we're really not sure the fertilizer was
responsible for the excellent growth.
1.
List three additional factors that could have affected the growth of the rose bushes, in addition
to the fertilizer.
Since there are many possible factors that could have affected the growth of the roses, it would be
useful if we could compare my neighbor's results with a control group. A control is a group of test
subjects (in this case rose bushes) that are the same species, living in the exact same conditions,
receive the same amount of sunlight, get the same amount of water, everything the same. The only
difference between the two groups is that one group gets fertilizer and the other doesn't. That way if
there is a measurable growth difference between the two groups, I know it was due to the fertilizer,
because there was no other difference between the two groups of rose bushes.
The same thing would hold true if I was testing a new blood pressure medicine. You need a control
group as a standard for comparison to make sure that your results are due specifically to the factor you
are trying to test for. The factor being investigated in a particular experiment is called a variable.
In the case of a medical experiment, it is really hard to make the control group exactly the same as the
experimental group. For example, if you give the experimental group medication in pill form, the
control group has to take an identical pill (without the medication). I was listening to an interesting
program a couple of weeks ago about how difficult it was to design the fake medications (called
placebos). For example, if the real medicine tastes bitter, the placebo pill has to be bitter also, so no
one will know whether they are getting the real medicine or not.
Consider the following experiment.
A vitamin company wants to determine whether large doses of vitamin C would shorten the length of
time it takes to recover from a cold. The company hires 300 people and splits them into two groups.
The distribution of people in each group is similar with regard to age, weight, height, gender, etc. For
the first ten days of the experiment, Group A is given a daily dose of 4 g of vitamin C (in a pill). Over
the same ten days, Group B is given a similar size pill with no vitamin C content. None of the people
in either group know which pill they are receiving. In addition, the scientists analyzing the results of
the experiment don't know which people have been assigned to Groups A and B.
On day one of the experiment, both groups are exposed to the cold virus by nasal swab. Researchers
track the patients in both groups for the presence of cold symptoms.
In regard to the vitamin C experiment:
2.
What variable is being tested?
3.
Which is the control group?
4.
Which is the experimental group?
5.
Why did the researchers try to make sure the people in the two groups were similar in age,
weight, health, etc.?
6.
Why is it important that neither the test subject nor the scientists analyzing the results knew
which people actually took the vitamin C?
ACTIVITY 3 - COLLECTING DATA AND ANALYZING THE RESULTS
When your hand is spread wide, the distance from the tip of your thumb to the tip of your little finger
is called your hand span. Hand span differs among individuals. In this activity, you will be collecting
hand span measurements and looking for patterns in the results.
1.
Using a metric ruler, measure the hand span of your right hand, and record the results in the
appropriate column of Table 1-1 below.
TABLE 1-1. HAND SPAN MEASUREMENTS
Hand Span (cm) - Males
Hand Span (cm) - Females
2.
Measure the hand spans of five additional adults, to produce a total of three measurements for
males and three for females.
3.
Post your results in the online classroom as directed by your instructor.
4.
Tabulate the pooled class results in Table 1-2.
TABLE 1-2. CLASS RESULTS
Hand Span
(cm)
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
other
TOTALS
Number of Males with Each
Hand Span
Number of Females with
Each Hand Span
Considering the pooled results for the class, answer the following questions.
5.
What is the most frequent hand span among males? _____________ cm
What is the most frequent hand span among females? _____________ cm
Within a set of numbers, the number that occurs most frequently is referred to as the mode. Knowing
the mode can be useful in many situations. For example, if you were the purchasing officer for a large
shoe store, knowing the mode would help you decide what quantity of a specific shoe size you should
buy to meet customer demand.
6.
Subtract the smallest male hand span from the largest male hand span.
The difference in male hand span is ________ cm.
The difference between the largest and smallest numbers in a set is referred to as the range. This is a
measure of how diverse (or spread out) the numbers are. For example, if there was a wide range of
housing prices in your area, this could indicate that people with a variety of incomes live there.
7.
Calculate the range of female hand spans. The range is ________ cm.
Does the range differ from your calculations for males? If so, how is it different?
8.
To calculate the average hand span, also called the mean, add up all the hand span
measurements collected for one gender. Then divide by the total number of people of that
gender that were measured.
average hand span for males __________ cm
average hand span for females __________ cm
9.
Using the mean, you can answer several questions. For example:
Is there a difference between the average male and female hand span? If so, describe the
difference.
Is your hand span typical for your gender? __________
If not, is your hand span smaller or larger than average? ____________
10.
Write out all the male hand span measurements in order from smallest to largest. If more than
one person had the same hand span, record that number multiple times. Your list of numbers
will look something like this:
15
16
16
17
17
17
18
19
20
20
20
20 etc.
This set of numbers is needed to determine the median. The median is the middle number of a
set.
If there are two numbers in the middle of your set (for example, if your set has ten numbers),
average the middle two numbers to determine the median.
ACTIVITY 4 - GRAPHING YOUR DATA
A graph is a visual way of presenting your data. The purpose of a graph is to make it easier for
someone to understand the information you want to express. Since graphs make it easier to present a
lot of information in a small space, graphs are used in every aspect of society. It is important,
therefore, that you are able to read a graph and interpret the data accurately. You should also be able
to recognize the characteristics of a good graph and incorporate them into graphs of your own.
A graph has an X (horizontal) axis and a Y (vertical) axis (see Figure 1-1).
Figure 1-1. The X and Y Axes of a Graph
A good graph shows the units of measurement and an explanation for both axes and has a title that lets
the reader know what the graph is about.
In addition, when the points are plotted, they should be distributed along most of the X and Y axis.
Both axes should begin and end with numbers that are pretty close to the smallest and largest data
points. To see an example of this type of data distribution, examine the distribution of the graphed
points Figure 1-2.
Figure 1-2. A Properly Constructed Graph
1.
How many data points were plotted in Figure 1-2? ____________
2.
Which size hand span represents the mode? _______________
3.
What is the smallest hand span that was measured? ______________
What is the largest? _________________
Figure 1-3. Sample Graph.
4.
List three items that should be corrected to improve the presentation of the information in the
Figure 1-3. Explain your reasoning for each correction.
a.
b.
c.
5.
Draw a graph showing the data the class collected during the hand span investigation. Prepare
the graph on a computer using the instructions provided by your instructor.
Submit the graph as required by your instructor.
EXERCISE 1 - SCIENTIFIC METHOD
OBJECTIVES
After completing this exercise, you should be able to:
•
•
•
•
•
•
formulate a testable hypothesis
explain what a control is and why it offers validity to experiments
collect and organize data for analysis
calculate the mean, median, mode, and range for a set of data
construct graphs that clearly and accurately represent a set of data points
identify the characteristics of well constructed versus poorly constructed graphs
SUPPLIES
Activity 3
one 30 cm long metric ruler
ACTIVITY 1 - STEPS OF THE SCIENTIFIC METHOD
When scientists approach a question or a problem, they do it in a very simple and structured way. In
general, the process that scientists use in answering questions uses the following steps:
•
•
•
•
•
Observation
Develop Hypothesis
Design Experiment to Test Hypothesis
Collect Data and Analyze Results
Conclusion
Once a conclusion is reached, that's not the final answer. Conclusions are always subject to review and
interpretation as more information is collected about the topic. If the results don't support the original
hypothesis, scientists will usually form a new hypothesis and try again.
You've heard the word hypothesis many times, but what is it? How is a hypothesis developed? A
hypothesis is an educated guess, based on facts. A hypothesis must be based on evidence, even if that
evidence is simply your own prior experience. Therefore, it must be logical.
A good hypothesis has two essential feature: it is specific and it is testable. The more specifically the
hypothesis is stated, the easier it is to develop a method to confirm or reject the hypothesis.
For example, if you misplaced your homework, a bad hypothesis might be "the dog ate it," because this
would be both unlikely and difficult to confirm. A better hypothesis might be "I left it in the computer
lab or I left it in the car," because these are quite simple to test, and are very specific.
Mark all the "bad" or poorly framed hypotheses in the following list. Rewrite each hypothesis that you
marked into an acceptable format.
1.
_____
Spinach makes you stronger.
2.
_____
Adding fertilizer to tomato plants will cause them to produce more fruit.
3.
_____
Susan will lose weight by taking Quick-Loss Diet Pills.
4.
_____
Soft contact lenses are better than hard contact lenses.
ACTIVITY 2 - DETAILS OF AN EXPERIMENTAL SETUP
Once you have developed a hypothesis, you may wish to test your hypothesis with an experiment. In
science, experiments must be designed in a specific way, so that the results will be accurate. One facet
of these procedures is the concept of a control.
I looked into my neighbor's yard and notice that his rose bushes are big and bushy and covered with
flowers. I say to him, "How did your roses grow so big?" He replies that he fertilized the bushes. I
say, "Great. I can do the same to make my bushes as wonderful as yours, but, by the way, how can
you be sure that the fertilizer was the cause of all this growth?" And he says to me, "Gosh I really
don't know for sure. I fertilized them and they grew pretty well this year. I guess that the fertilizer
caused this excellent growth." And I reply, "Are you sure it wasn't because we had more rainfall this
year? Or that the weather wasn't as hot as usual?" So, we're really not sure the fertilizer was
responsible for the excellent growth.
1.
List three additional factors that could have affected the growth of the rose bushes, in addition
to the fertilizer.
Since there are many possible factors that could have affected the growth of the roses, it would be
useful if we could compare my neighbor's results with a control group. A control is a group of test
subjects (in this case rose bushes) that are the same species, living in the exact same conditions,
receive the same amount of sunlight, get the same amount of water, everything the same. The only
difference between the two groups is that one group gets fertilizer and the other doesn't. That way if
there is a measurable growth difference between the two groups, I know it was due to the fertilizer,
because there was no other difference between the two groups of rose bushes.
The same thing would hold true if I was testing a new blood pressure medicine. You need a control
group as a standard for comparison to make sure that your results are due specifically to the factor you
are trying to test for. The factor being investigated in a particular experiment is called a variable.
In the case of a medical experiment, it is really hard to make the control group exactly the same as the
experimental group. For example, if you give the experimental group medication in pill form, the
control group has to take an identical pill (without the medication). I was listening to an interesting
program a couple of weeks ago about how difficult it was to design the fake medications (called
placebos). For example, if the real medicine tastes bitter, the placebo pill has to be bitter also, so no
one will know whether they are getting the real medicine or not.
Consider the following experiment.
A vitamin company wants to determine whether large doses of vitamin C would shorten the length of
time it takes to recover from a cold. The company hires 300 people and splits them into two groups.
The distribution of people in each group is similar with regard to age, weight, height, gender, etc. For
the first ten days of the experiment, Group A is given a daily dose of 4 g of vitamin C (in a pill). Over
the same ten days, Group B is given a similar size pill with no vitamin C content. None of the people
in either group know which pill they are receiving. In addition, the scientists analyzing the results of
the experiment don't know which people have been assigned to Groups A and B.
On day one of the experiment, both groups are exposed to the cold virus by nasal swab. Researchers
track the patients in both groups for the presence of cold symptoms.
In regard to the vitamin C experiment:
2.
What variable is being tested?
3.
Which is the control group?
4.
Which is the experimental group?
5.
Why did the researchers try to make sure the people in the two groups were similar in age,
weight, health, etc.?
6.
Why is it important that neither the test subject nor the scientists analyzing the results knew
which people actually took the vitamin C?
ACTIVITY 3 - COLLECTING DATA AND ANALYZING THE RESULTS
When your hand is spread wide, the distance from the tip of your thumb to the tip of your little finger
is called your hand span. Hand span differs among individuals. In this activity, you will be collecting
hand span measurements and looking for patterns in the results.
1.
Using a metric ruler, measure the hand span of your right hand, and record the results in the
appropriate column of Table 1-1 below.
TABLE 1-1. HAND SPAN MEASUREMENTS
Hand Span (cm) - Males
Hand Span (cm) - Females
2.
Measure the hand spans of five additional adults, to produce a total of three measurements for
males and three for females.
3.
Post your results in the online classroom as directed by your instructor.
4.
Tabulate the pooled class results in Table 1-2.
TABLE 1-2. CLASS RESULTS
Hand Span
(cm)
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
other
TOTALS
Number of Males with Each
Hand Span
Number of Females with
Each Hand Span
Considering the pooled results for the class, answer the following questions.
5.
What is the most frequent hand span among males? _____________ cm
What is the most frequent hand span among females? _____________ cm
Within a set of numbers, the number that occurs most frequently is referred to as the mode. Knowing
the mode can be useful in many situations. For example, if you were the purchasing officer for a large
shoe store, knowing the mode would help you decide what quantity of a specific shoe size you should
buy to meet customer demand.
6.
Subtract the smallest male hand span from the largest male hand span.
The difference in male hand span is ________ cm.
The difference between the largest and smallest numbers in a set is referred to as the range. This is a
measure of how diverse (or spread out) the numbers are. For example, if there was a wide range of
housing prices in your area, this could indicate that people with a variety of incomes live there.
7.
Calculate the range of female hand spans. The range is ________ cm.
Does the range differ from your calculations for males? If so, how is it different?
8.
To calculate the average hand span, also called the mean, add up all the hand span
measurements collected for one gender. Then divide by the total number of people of that
gender that were measured.
average hand span for males __________ cm
average hand span for females __________ cm
9.
Using the mean, you can answer several questions. For example:
Is there a difference between the average male and female hand span? If so, describe the
difference.
Is your hand span typical for your gender? __________
If not, is your hand span smaller or larger than average? ____________
10.
Write out all the male hand span measurements in order from smallest to largest. If more than
one person had the same hand span, record that number multiple times. Your list of numbers
will look something like this:
15
16
16
17
17
17
18
19
20
20
20
20 etc.
This set of numbers is needed to determine the median. The median is the middle number of a
set.
If there are two numbers in the middle of your set (for example, if your set has ten numbers),
average the middle two numbers to determine the median.
ACTIVITY 4 - GRAPHING YOUR DATA
A graph is a visual way of presenting your data. The purpose of a graph is to make it easier for
someone to understand the information you want to express. Since graphs make it easier to present a
lot of information in a small space, graphs are used in every aspect of society. It is important,
therefore, that you are able to read a graph and interpret the data accurately. You should also be able
to recognize the characteristics of a good graph and incorporate them into graphs of your own.
A graph has an X (horizontal) axis and a Y (vertical) axis (see Figure 1-1).
Figure 1-1. The X and Y Axes of a Graph
A good graph shows the units of measurement and an explanation for both axes and has a title that lets
the reader know what the graph is about.
In addition, when the points are plotted, they should be distributed along most of the X and Y axis.
Both axes should begin and end with numbers that are pretty close to the smallest and largest data
points. To see an example of this type of data distribution, examine the distribution of the graphed
points Figure 1-2.
Figure 1-2. A Properly Constructed Graph
1.
How many data points were plotted in Figure 1-2? ____________
2.
Which size hand span represents the mode? _______________
3.
What is the smallest hand span that was measured? ______________
What is the largest? _________________
Figure 1-3. Sample Graph.
4.
List three items that should be corrected to improve the presentation of the information in the
Figure 1-3. Explain your reasoning for each correction.
a.
b.
c.
5.
Draw a graph showing the data the class collected during the hand span investigation. Prepare
the graph on a computer using the instructions provided by your instructor.
Submit the graph as required by your instructor.

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