Scientific Method Study Guide KEY
Part I. Scientific Method Vocabulary
Directions: Write the word in the blank to the left that matches the definition.
Word Bank: Measurement Bias, Sampling Bias, Theory, Hypothesis, Variable, Control, Independent
Variable, Dependent Variable, Scientific Method, Experimental Errors, Reliable,
____Theory_______________ 1. A well-tested explanation to a problem based on much evidence.
____Variable______________ 2. Any factor, trait, or condition that can exist in differing amounts or
types.
____Scientific Method______ 3. An organized process used in science to answer questions/problems.
____Independent Variable___ 4. The variable that is purposely changed in an experiment.
____Hypothesis___________
5. An explanation to a problem based on prior knowledge, personal
experiences, and observations.
____Dependent Variable____ 6. The variable that depends on the independent variable (usually what
you are measuring).
____Control______________
7. The variable without any changes.
____Experimental Errors____
8. Mistakes that occur during the experiment that may affect the
results.
____Reliable_____________
9. When you can trust your results, your experiment is said to be
____Sampling Bias________
10. When the number of people you surveyed in your experiment does
NOT represent the entire population you are interested in
Part II. Question and Hypothesis
Read the following situations. Identify the question and write a testable hypothesis for each situation
1.
Mom and I were baking a cake for my brother’s birthday. We didn’t have any baking powder.
The recipe said to add one teaspoon of baking powder to the cake batter. Since that’s such a
small amount we baked the cake anyway. We were very disappointed when the cake came out
flat instead of fluffy. We think maybe we needed to add the baking powder.
Question/Problem:
Is baking soda the ingredient that makes a cake rise?
Does backing soda make a cake rise?
Hypothesis:
When you don’t put baking soda in cake batter, the cake will not rise.
When you do put baking soda in cake batter, the cake will rise.
2.
You and your friends were studying lists of spelling words and vocabulary words. It seemed like
everyone could easily remember the first word on the list and the fifteenth word on the list. It
seemed very hard to remember the words in the middle of the list.
Question/Problem:
Why is it difficult to remember the words in the middle of a list?
Why is it easy to memorize the first and last word of a list?
Hypothesis:
It is difficult to remember the words in the middle because the words have not been stored into
your long term memory nor are they stored in your short term memory.
It is easy to memorize the first and last word of a list because the first word is stored into your
long term memory and the last word is still in your short term memory.
3. The Acme cleansers Company wants to do some advertising for its new anti-bacterial kitchen
cleaner. The advertising executives want to run some tests that show that their new product is
better than the best-selling brand of kitchen cleaner.
Question/Problem:
Which cleaning product is better? Acme cleaner or the best-selling kitchen cleaner?
Is the new Acme Cleaner better than the best-selling kitchen cleaner?
Hypothesis:
Acme cleaner is the best kitchen cleaner.
Acme cleaner is not as good as the best-selling kitchen cleaner.
Part IV. Bias
1. What is the similarities and differences between sampling bias and measurement bias?
Both sampling bias and measurement bias in an experiment will cause the results to be
UNRELIABLE. An experiment with bias will not represent the actual truth. Sampling bias occurs
when the sample being “measured” is not appropriate for what is being measured. Sampling
bias can include, gender, age, location, and number of samples is not enough. Measurement
bias occurs when the WAY the data is collect will cause to the studies of the results to not match
what is true in reality. This can include inappropriate measure tools and/or misleading
questions.
2. Give an example of sampling bias.
An example of sampling bias is if I wanted to know what students at Merced High felt was the
best movie this summer and I only asked girls.
3. Give an example of measurement bias.
An example of measurement bias is if I wanted to know what students at Merced High felt was
the best movie this summer and I asked 100 random students “Which movie had more action?
The Dark Knight Rises or Hunger Games?” This is an example of measurement bias because my
results will show which movie had more action instead of which movie was actually better.
Part V. Experimental Design
The Strange Case of BeriBeri
In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was beriberi.
Symptoms of the disease included weakness and loss of appetite, victims often died of heart failure.
Scientists thought the disease might be caused by bacteria. They injected chickens with bacteria from
the blood of patients with beriberi. The injected chickens became sick. However, so did a group of
chickens that were not injected with bacteria.
One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten
whole-grain rice, but during the experiment, the chickens were fed polished rice. Dr. Eijkman researched
this interesting case and found that polished rice lacked thiamine, a vitamin necessary for good health.
1. State the Problem
What was causing strange nerve disease in Dutch East Indies?
There is actually a second question to this experiment: What was causing the chickens that
were not injected to get sick?
2. What was the hypothesis?
The disease in Dutch East Indies was caused by bacteria.
3. What is the independent variable?
Whether or not the chickens received the bacteria extracted from patients with beriberi.
4. What is the dependent variable?
Whether or not the chicken’s got sick from the beriberi bacteria.
5. What is the control?
The chickens that did not receive the beriberi bacteria.
6. Should the hypothesis be supported or rejected based on the experiment?
It should be rejected because the results in the chicken experiment showed that the bacteria
was NOT causing the deaths of the chickens.
7. What should be the new hypothesis and how would you test it?
The new hypothesis should be “Polished rice is causing the strange nerve disease in Dutch East
Indies because the polished rice does not have thiamine”. I would test this by having two
groups of chickens. In the first group, the chickens would eat the whole-grain rise and in the
second group, the chickens would eat the polished rice.