Name _________________________________________ Date _________

Review Packet for Scientific Method Unit Exam

Terms related to the parts of a controlled experiment: Match the term with its definition.

__A___controlled experiment

A) sets up experimental groups to determine how two factors are related. In

the experiment, all factors must be the same in every way possible except for

one variable that is tested (independent variable.)

__F___variable

B) the factor that you measure to gather your results.

_D____independent variable

C) a testable explanation for your problem. It is stated in an If and then

format.

_B____dependent variable

D) the variable that is manipulated or changed by the scientist. It is also called

the experimental variable.

_C____hypothesis

E) occurs when an organism is in a balanced, steady state and is healthy.

_H____constants

F) any factor in a controlled experiment that can change.

_G____control group

G) a group that is tested with “normal” conditions, without the independent

variable, and used for comparison.

_E____homeostasis H) are all of the factors that are the same in all the subjects of the experiment.

An Example of a Controlled Experiment: A scientist wants to study the effect of the amount of sunlight on plant growth. She puts plants in a room

with no sunlight, plants in a room with direct sunlight, and plants in a room with indirect sunlight. She

records the height of the plants at the beginning of the month and at the end of the month.

How do we analyze the experiment?

In this experiment, the independent variable is the amount of light the plants received. The dependent

variable is the amount of plant growth measured. The constants are the same in all three rooms: type and

age of all plants, amount of water they receive daily, and temperature and humidity levels. The controlled

group is the plants in the room with the indirect sunlight (normal conditions.)

The Scientific Method: Analyzing the Parts of an Experiment:

Experiment #1

Karen does an experiment to see what kind of two fertilizers she uses will make her plant grow faster. She

bought the “Stop and Shop” brand and “Miracle Grow” brand and put the same amount into two identical

plants. They were put on the same window sill. She wanted to see which one would grow faster after two

weeks.

These were her observations, which she recorded in the following data chart:

Fertilizer Brand Growth after one week(cm)

Stop and Shop 3cm

Miracle Grow 7cm

Answer the questions that follow based on Karen’s experiment.

1. What is the proper

way to write a

hypothesis? Write a hypothesis

for Karen’s

experiment

If the ____________________ (increases, ) then the _____________ would

____________________, ___________________, or _________________.

If Stop and Shop fertilizer is used, then the plant

will grow faster.

2. What is the

independent

variable.

(Remember: “I

change…”)

Type of fertilizer (Miracle Grow/ Stop and Shop

fertilizer)

3. What is the

dependent variable.

( Remember: D for

data)

What measuring tool

should she use to

collect her data?

How fast the plant grows.

How tall the plant grows in one week.

4. What are the

constants in this

experiment?

(Remember: S for

“the same”)

Same plant

Same window sill

Same amount of fertilizer in each plant

5. Karen is missing a

control group. What

should she do?

A plant with NO FERTILZER

6. What do we mean

by the validity of an

experiment? What

would make this

experiment more

valid

How true the results are.

Larger sample size, control group, more trials

7. What is the

sample size of this

experiment?

Should it be small or

large? Why

2 plants!!!!

LARGE!!!

8. What is Karen’s

conclusion for this

experiment?

The plant given Miracle Grow grows faster. It

grew to 7 cm.

Experiment #2:

A student buys a new electronic toy. In the store he notices different brands of batteries. He wants to know

which battery will last the longest, so he designs a controlled experiment. He buys four types of batteries.

One type of battery is placed into the toy. He records the exact number of minutes the toy works until the

battery runs out. Then he replaces the battery with a different type of battery, and again records the time it

takes for the battery to run out. He repeats it for all four brands of batteries.

Independent variable ___TYPE OF BATTERY_____________

Dependent variable ___MINUTES THE TOY WORKS_____

Constants ___SAME TOY

Experiment #3:

A teacher would like to know if increasing the amount of homework problems each night will increase her

students’ performance on tests. She decides to give 5 extra homework problems each night to 2 of her 5

classes, and 10 extra homework problems to the other 2 classes. The 5th class will get no extra homework.

She will measure the performance of the students on the test the following week.

Identify the following:

Problem DOES INCREASING THE AMOUNT OF

HOMEWORK PROBLEMS INCREASE TEST

PERFORMANCE? Hypothesis IF A CLASS IS GIVEN MORE HOMEOWRK,

THEN THEY WILL SCORE HIGHER ON THE

TEST. Independent variable AMOUNT OF HOMEOWRK

Dependent variable THE TEST GRADES

Constants SAME TYPE OF PROBLEMS, GIVEN ON

SAME NIGHT, GIVEN SAME TEST

Control group The 5th CLASS GIVEN NO HOMEWORK

Graphing: A biology class conducted an experiment to determine the rate of respiration of yeast in bread dough at

various temperatures. Bread dough will rise due to the production of carbon dioxide by the yeast present in

the dough. An equal amount of dough was placed in the bottom of each of five graduated cylinders. Each

cylinder was then placed in a different water bath to maintain a particular temperature. A diagram of the

setup is shown below.

The amount of expansion of the dough in each cylinder was measured after 15 minutes.

The results are shown in the data table below.

Directions (10–11): Using the information in the data table, construct a line graph on the grid, following the

directions below.

10. Mark an appropriate scale, without any breaks, on the axis labeled “Temperature of Water Bath (°C).”

11. Plot the data from the data table. Surround each point with a small circle and connect the points.

Measuring: 1. What is the approximate length of the earthworm shown in the diagram below?

(1) 9 mm (3) 10.6 cm

(2) 90 mm (4) 106 cm

2. A= _______0.6_____cm = ____.006__________ m

3. D= ______3.7______cm = ____.000037________km

4. F= ______6.7_______cm = _____67___________mm

3. ______21.5____________________ mL

21.5

4. _______44______ °C

cm

There is no control group. There is no

group NOT given the Auxin/Growth

Hormone

15 shrews

How to solve: Find 500,000 on the x-axis, read up to where it meets your line for

shrews (with circles), read across to find the answer on the y-axis.

1. Which statement about the use of independent variables in controlled experiments is correct?

(1) A different independent variable must be used each time an experiment is repeated.

(2) The independent variables must involve time.

(3) Only one independent variable is used for each experiment. (4) The independent variables state the problem being tested.

2. The development of an experimental research plan should not include a

(1) list of safety precautions for the experiment

(2) list of equipment needed for conducting the experiment

(3) procedure for the use of technologies needed for the experiment

(4) conclusion based on data expected to be collected in the experiment

3. A biologist used the Internet to contact scientists around the world to obtain information about declining

amphibian populations. He was able to gather data on 936 populations of amphibians, consisting of 157

species from 37 countries. Results showed that the overall numbers of amphibians dropped 15% a year from

1960 to 1966 and continued to decline about 2% a year through 1997.

What is the importance of collecting an extensive amount of data such as this?

(1) Researchers will now be certain that the decline in the amphibian populations is due

to pesticides.

(2) The data collected will prove that all animal populations around the world are threatened.

(3) Results from all parts of the world will be found to be identical.

(4) The quantity of data will lead to a better understanding of the extent of the

problem.

4. The first trial of a controlled experiment allows a scientist to isolate and test

(1) a logical conclusion

(2) a variety of information

(3) a single variable

(4) several variables