Different types of investigations
• Controlled experiments
– A lab investigation in which the values of all variables are kept the
same except for one that is changed from experiment to
experiment (manipulated variable) and one that is measured
(responding variable).
– Have experimental and control groups
– Include at least 3 levels of manipulated variable (if measuring
effect of fertilizer on plant growth, use 10 g., 20 g. and 30 g. of
fertilizer on different plants)
– Include at least 3 trials for each condition (can be repetitions or
more subjects).
• Field study
– A scientific study of free-living plants or animals in which the
subjects are observed in their natural habitat without changing,
harming, or altering the setting or subjects.
– No experimental and control groups
– May include sampling, observation, etc.
Variables
https://www.youtube.
com/watch?v=VhZyX
mgIFAo&noredirect=1
Responding (dependent) variable: The variable they you are measuring
Manipulated (Independent): The variable you are changing
Controlled variables: All the variables that stay the SAME
** only one variable is changed at a time
Experimental Control: The experimental control is the experiment done
without the "variable". The variable is the thing that you are changing to
see what happens.
A control group's purpose is to make sure that any observed results are
statistically related to the tests being performed, and not simply random
occurrences that happen anyway
Controlled variables
Experimental Control
Reliability & Validity
Reliability: An attribute of any investigation that promotes
consistency of results during repeated trials.
Validity: An attribute of an investigation that describes the degree of
confidence that data collected and logical inferences are accurate
representations of the phenomena being investigated.
• Reliability –
– Increased by repeating an investigation = more trials
• Validity –
– Increased by:
•
•
•
•
Adding more controlled variables
Improving measuring technique
Controlling for sample bias
Including an experimental control group
Complete Worksheet Together
Conclusion Items
• Foaming Spuds Conclusion
– 5 attributes
– New attribute- Scientific Explanation
5
Conclusion Format
There are 4 sentence starters that you MUST have
to write an accurate conclusion.
1. The Prediction was…
2. When… then…
3. The data shows…
4. When comparing the data we find…
5. Scientific Explanation
1. The Prediction that … (restate hypothesis/supported or rejected)
Example: The prediction that increasing the amount of watering a plant will increase plant growth
was supported by the data.
2. When…Then… (What actually happened)
Example: When we increased the amount of watering, then the plants grew more.
3. The data shows… (has 3 parts)
• First, you need to pick out the high and the low avg. responding data from the data table
and discuss it in terms of the manipulated variable
• second, you will also need to attach the word “only” to the low responding variable.
Example: The data shows that when the garden was watered for 2 hours a day the plants grew an
average of ONLY 4.6 cm a week, but when the garden was watered for 6 hours a day the plants
grew an average of 6.6 cm a week
4. When comparing the data we find that…
• First, you find the difference between the high average data, and the low average data. (do
the math)
• Second, you use comparing words to describe the difference. (higher, lower, hotter,
• Third, you include the manipulated context.
Example: When comparing the data we find that when the garden was watered for 6 hours a day,
the plants grew an avg of 2 cm taller than the plants in the garden that were watered for only 2
hours a day.
5. Scientific Explanation
Example: A possible scientific explanation for this is that plants need water for photosynthesis and
an increased amount of water will increase the productivity of photosynthesis.
An experiment was carried out to test the following hypothesis:
If I leave the tailgate down, then I will get better gas mileage because
it will make the shape of the car more aerodynamic
1. The Prediction was…
2. When… then…
3. The data shows…
4. When comparing the data we find…
5. Scientific Explanation
The prediction that if I leave the tailgate down, then I will get better gas
mileage was not supported by the data. When the car had the tailgate in
the up position, then the average gas mileage was higher. The data
shows that when the tailgate was in the up position the average gas
mileage was 20 mpg, but when it was all the way down it was only 18
mpg. When comparing data we find that when the tailgate was up it had
an average of 2 mpg more than when it was down. One possible
scientific explanation for this is that cars are manufactured and
designed to maximize fuel efficiency and having the tailgate up
makes the vehicle the most aerodynamic.
New Procedure Items
• Foaming Spuds New Procedure
– 7 attributes
– Extra Validity measure
– Experimental Control Condition (when appropriate)
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Field Study Scenarios & Items
• Field Study Template 7 Attributes
– Similar to controlled investigations but…
– Need to have 3 “conditions” instead of one controlled
variable
– Example: Which surface on the school campus will get
hotter?
• Compare asphalt, bare soil, and grass
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Maximize your points!
SHORT ANSWER
• Answer both bullets when there are two. Example:
– Describe two ways to solve the problem. In your
description be sure to:
• Identify two solutions to the problem
• Describe how each solution will solve the problem
• Students very often identify two solutions to the problem,
but do not attempt the second bullet. They generally must at
least attempt to address the second bullet to earn any points.
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Maximize your points!
CONCLUSIONS
• Write a complete comparison – don’t write, “the amount of
water does have an effect on the plant height.” Instead, say:
– Plant A grew the tallest;
– Plant A grew taller than plant B and plant C;
– The more water the plant had, the taller the plant grew.
• Include supporting data and/or descriptive text from the data
table.
– Quote from the data table.
– Be specific – cite data exactly as given in tables.
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Maximize your points!
NEW PROCEDURES
• Be sure to write the steps for a procedure when asked, not a
conclusion or prediction.
• The manipulated (independent) and responding (dependent)
variables don’t need to be specifically named or listed (e.g.,
Manipulated variable is water temperature) to receive credit
for them; the variables just need to be used correctly in the
procedure to be credited.
• Sometimes students switch the identities of the manipulated
and responding variables and contradict their procedure.
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Maximize your points!
NEW PROCEDURES
• Be very clear about what you are measuring.
• Many students write “record the data,” “measure the data,”
or “watch what happens and record the measurements”
without actually stating the responding variable. They should
write things like “record the number of organisms in the
sample area,” “measure the height of the plant,” or “measure
the time for seeds to germinate” to earn credit for the
responding variable.
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Maximize your points!
NEW PROCEDURES
• Write procedures that use the manipulated (independent)
and responding (dependent) variables given in the new
experimental or field study question.
• Don’t use the same responding variable as was used in the
original scenario. A procedure that does not use the correct
manipulated variable cannot answer the investigative
question and no points can be earned on the item.
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Inquiry Packet