Scientific Methods

Steps scientists use to answer questions and solve problems

Solving a Problem

Ask Question (Problem)

Gather Information

State Hypothesis

Design Experiment

Make Observations

Collect and Analyze Data

Form Conclusions

Retest (validate)

Solving a Problem

Ask a Question How does fertilizer affect the growth

rate of plants? scientists notice something in their

natural world Example: Does fertilizer make plants grow

taller?

Make Observations Gathered using the 5 senses

Record what happens during the experiment in your lab notebook

Use black or blue ink The information you write down is called data

Example: My neighbors’ plants are taller than my plants. He uses fertilizer and I do not.

State a Hypothesis A suggested solution to the problem

Must be testable Sometimes written as If…Then statement Predicts an outcome

Example: If plants are grown using fertilizer, then they will grow taller.

Design an Experiment A procedure to test the hypothesis

set up an experiment testing different amounts of fertilizer on plants & measuring the growth (height) of the plants must contain variables and controls may have many controlled factors can only change one variable

Design an Experiment Controls

factors that are kept constant not being tested! examples: amount of water, type of soil,

amount of sunlight, type of fertilizer act as a standard of comparison should not effect the outcome of the

experiment

Design an Experiment Variables

2 types 1- dependent variable

what you measure in the experiment unpredictable change: we don’t know how it will change until we do

the experiment graph on Y-axis

height of plants

2- independent variable manipulated variable predictable change: it only

changes because we chose how it would change

the more trials… the better graph on X-axis

amount of fertilizer

The effect of _____________

on _____________

INDEPENDENT

DEPENDENT

The effect of _____________

on _____________

Amount of Fertilizer

Height of Plants

Collect and Analyze Data May be organized into

charts, graphs, tables 2 types of data

Quantitative Expressed

mathematically numbers

Qualitative Descriptive nature

words, feelings

Analyze Data What does your data show

Graphs line graphs graphing data that shows continuous change bar graphs (or histograms) graphing data that is in disconnected groups

How’s a critterto choose?

Examples of experiments What’s the favorite drink of students?

we set up an experiment surveying students and asking which is their favorite drink : dependent variable (Y-axis)?

number of students

independent variable (X-axis)? type of drink

The effect of _____________

on _____________

Type of Drink

How many students chose it

Which drink do you like best?

type of drink

nu

mb

er

of

stu

den

ts

1

2

3

4

5

6

Coke Pepsi water tea Gatorade0

drink number

Coke 1

Pepsi 1

Water 4

Iced tea 4

Gatorade 3

Red Bull?

RBRB

Bar graph!

How does elevation affect temperature?

elevation

tem

pe

ratu

re

5

10

15

20

25

30

0 500 1000 1500 2000 25000

elevation (feet above sea level)

temp.

(°C)

0 30

500 25

1000 20

1500 15

2000 10

2500 5

1200 ft?

18

Line graph!

1200

Form Conclusions Answer to the hypothesis based on the

data obtained during the experiment Check for bias In order to verify the results,

experiments must be Retestedvalid! Communicate results

Scientists publish work in journals

Any Questions??

Examples of experiments How does exercise affect heart rate of

10th grade student? we set up an experiment testing

different lengths of time of exercise (minutes) on the heart rate of students: dependent variable (Y-axis)?

heart rate

independent variable (X-axis)? minutes of exercise

The effect of _____________

on _____________

Exercise

Heart Rate