LEH U2 00 Scientific Method 2014

(1)

Scientific Method

(2)

Scientific Theory

A

theory

is an explanation of a set of related

observations or events, supported by proven

experiments, and verified multiple times by

many independent scientists.

(3)

How Does a Theory

differ from a Law?

(4)

Observation vs.

Inference

• Observation:

(5)

Observation vs.

Inference

• _Inference:

(6)

Steps in the Scientific

Method



Observation

_Observation



State the

_{State the}

Problem



Hypothesis

_Hypothesis



Experiment

_Experiment



Data Collection

_{Data Collection}



Conclusion

_Conclusion

(7)

Observation



_{How would you explain what you see?}



_{Plants grow differently in differently colored}

(8)

1. State the

Problem



_{What problem are you trying to solve?}



_{Always write it as a}

_question

_{beginning with}

DOES

or

WILL

….?



_{Ex. Does red light affect the growth of a}

(9)

2. State Your Hypothesis



_{Hypothesis = an}

_{educated guess}

_.



_{Written as --- If….then}

_statement

_.



_{Hypothesis must be}

_testable

_.



_{Ex. If the red light is used, then}

(10)

Example situations –

Using Temperature

and Breathing Rate

(11)

Here are some

possible

hypotheses.

Hypothesis:

If

the water temperature is increased,

(12)

Formulate a hypothesis on

the following topics:

1. Smoking

2. Global

Warming

3. Steroids

(13)

(14)

Set up a

Controlled Experiment

There are always

two groups

in an experiment:

• _{Experimental Group}

_{– receives the treatment, the}

“variable”

(15)

•A factor in the experiment that is being

changed

(16)

•The

independent

variable

is the one factor that

is

being

changed by

experimenter

(17)

What is the

dependent variable

then?



_{The variable that is measured}

in the experiment.

Ex. --- growth of a plant, breathing rate of the fish

(18)

All of the other

conditions that are kept the same

between the two groups.

(19)

Let’s Practice

Control group:

Experimental Group

:

Independent variable:

Dependent variable:

Constants:

Problem

: Does the water temperature

affect the breathing rate of the fish?

(20)

4. C

ollect Data

•Utilize a

chart, table or graph

to

organize data.

(21)

Graphing Basics

 _{Independent Variable}_{: - the cause. (the “if” of if, then)}

always plotted on the x-axis

- factor in the experiment that the experimenter changes

-you know the values before you begin the experiment

 _{Dependent Variable}_{:- the effect (the “then” of if, then)}

always plotted on the y-axis

- factor that is measured as the experiment proceeds

(22)

pH

Plant Growth

after 1 hour

Plant Growth

after 2 hours

Plant Growth

after 2 hours

Plant Growth

after 3 hours

Plant Growth

after 3 hours

2

2 10 cm.

10 cm.

15 cm.

22 cm.

4

4 6 cm.

6 cm.

12 cm.

15 cm.

6

6 5 cm.

5 cm.

10 cm.

12 cm.

8

8 4 cm.

4 cm.

9 cm.

10 cm.

10

(23)

A scientist is conducting an experiment to determine the

number of oxygen bubbles produced by plants at

varying levels below the surface of water.



What is the independent variable?



What is the dependent variable?



What is the title of the graph?



What will you label the x-axis?

(24)

5. Draw A

Conclusion

•Draw a conclusion

based on the data

.

(you should

reference your data, use #’s)

•Determine if your hypothesis was

(25)



_{Repeated trials}

_{- do the}

experiment many times for

valid results.



_{Large sample size}

_{– use}

many subjects for valid

results.

(26)

• _{Too Few Subjects:}

_{not a large}

enough sampling to draw a valid

conclusion from.

(27)

Question # 1



_{A new concept that is tested in a scientific}

investigation is known as

a.

A theory

b.

The hypothesis

c.

An inference

(28)

Question # 2



_{Which procedure must be followed for}

the results of an experiment to be

considered valid?

a.

The experiment must be repeated a number

of times and yield similar results.

b.

After one trial, the results of the experiment

must be published.

c.

The results must be expressed in the form of

a graph or table.

(29)

Question # 3



_{An investigation was designed to determine}

the effect of sunlight on mold growth. Two

groups of mold were grown under identical

conditions except that one group was

exposed only to sunlight, while the other was

grown in total darkness. In this

investigation, the group of mold grown

without receiving sunlight is known as the

a. Experimental variable b. Dependent variable c. Control

(30)

Question # 4



_{A biologist in a laboratory reports a new}

discovery based on experimental results. If the

results are valid, biologists in other laboratories

should be able to

a. Repeat the same experiment with a different variable and get the same results.

b. Perform the same experiment and obtain different results.

c. Repeat the same experiment and obtain the same results.

d. Perform the same experiment under different

(31)

Question # 5

 _{To test the effect of hormones (auxins) on plant growth,}

6 plant seedlings of the same species were measured and then sprayed with auxin (growth hormone). After 4 weeks of growth under ideal conditions, the plants were measured again. To set up a proper control for this

experiment, the investigator should

a. Spray the same plants with different amounts of auxin.

b. Spray auxin on 6 plant seedlings of the same species and grow them in the dark.

c. Wash the auxin off 3 of the plants after 2 weeks.

d. Grow another 6 plant seedlings of the same species under the same conditions, spraying them with