Introduction to Science
Scientific Method:
(6 steps)
1. Define the problem – usually stated as a question
2. Research and Observations – gather background information
3. Form a hypothesis, make predictions (If……, then……)
– Must be testable and measurable
4. Test the hypothesis – perform an experiment
Controlled Experiment – only one variable is being tested at a time (experimental variable)

Variable – factor in an experiment that can change
Ex: temperature, time, size, amount or kind of material

Variable that is deliberately changed – manipulated or independent variable (Typically the
manipulated or independent variable is also considered to be the experimental variable.)

Variable that changes in response to manipulated variable – responding or dependent variable

Experimental group – contains the variable being tested

Control group – does not contain the experimental variable
Ex: A scientist designs an experiment to see which kind of fertilizer causes the most growth in
tomato plants. He tests Scott’s Liquid Grow, Miracle-Gro, and Fertilome Super Grow. He also
tests one group of plants that do not receive any fertilizer. All plants are given the same amount
of water, sunlight and potting soil. The scientist measures the height of the plants every 2 days
for 14 days.
Experimental variable = kind of fertilizer
Control group = group that received no fertilizer
Manipulated (independent) variable = kinds of fertilizer
Responding (dependent) variable = plant height
5. Gather and analyze data from experiment
a. Data should be gathered from large sample sizes in order to be more representative
Ex: use many tomato plants (100+) when testing for fertilizers
b. The closeness of a measurement to the true value of what is being measured – accurate
Ex: Hitting close to or on the bulls eye of a target
c. Exact or repeated measurements very close in value – precise
Ex: Hitting close to or on the bulls eye of a target multiple times
6. Form a conclusion based on the data from the experiment
a. If data supports hypothesis – repeat the experiment for verification
b. A hypothesis tested and confirmed often enough that it is unlikely to be disproved becomes a
theory
c. If data does not support hypothesis – refine experiment, then repeat experiment
Organizing Lab Data:
Tomato Plant Growth
Date
Plant A Height
Plant B Height
Experiment
Graph
1. Data Tables – must have title, headings and be in chart form
2. Graphs – 3 types (line, bar, or pie graphs)
a. Manipulated or independent variable (variable the scientist purposely changes)
MIX – graphed on X-axis (horizontal axis)
b. Dependent or responding variable (variable that responds to what scientist changes or the
manipulated variable)
DRY – graphed on Y-axis (vertical axis)
D = Dependent
or
R = Responding
variable
Y = on Y axis
Good Graphs
1. Label axes – be specific, use units
a. time – hour, minutes
b. weight – pounds, grams
2. Numbers on axes must be in even increments and evenly spaced
a. 2, 4, 6, 8, 10
b. 5, 10, 15, 20
c. 1, 5, 7, 10, 12
WRONG!
3. Use at least 2/3 of available space both
horizontally and vertically
4. Title your graph – be specific and descriptive
5. When multiple data sets are graphed – use a
legend or key
6. Extrapolate data – beyond the data
7. Interpolate data – with the given data points
Ex:
Temperatures In NY City
Day
Temperature
1
43° F
2
53° F
3
50° F
4
57° F
5
59° F
6
67° F
M
I
X
Observation and Inference Notes
I.
Observation
Gathering data or information by using our senses. What are the senses?
A. 2 Types of Observations
1. Qualitative—descriptive (using adjectives)
Examples:

The apple is red.

The blanket feels soft.

The orange smells rotten.

The punch tastes very sweet.

We could hear a fizzing sound.
2. Quantitative—measurements with numbers and units or comparative measurements
Examples:

The pencil is 8.3cm long.

The apple has a mass of 85 grams.

There is 25 mL of water in the glass.

The apple is larger than rock.
II. Inference
A judgment based on observation and past experience.
The process of making a logical conclusion.
The act of reasoning from factual knowledge or evidence.
Examples:
There is water standing in a puddle. (ob)
It rained last night. (inf)
Your little brother, Billy, is holding your broken sunglasses. (ob)
He broke them. (inf)
There is a clear, colorless liquid in the beaker. (ob)
The beaker contains water. (inf)
Practice
Read each of the following observations and label as a qualitative (A) or quantitative (B) observation.
1. There are 14 M&M’s in the package.
___
2. The chocolate brownie is sweet and cheesy.
___
3. The spicy smell of gingerbread drifted from the kitchen.
___
4. Laura added 250 grams of melted chocolate to the bowl.
___
Observe the picture to the right. Determine if each of the
following statements is an observation (O) or an inference (I).
5. The dog has a large nose.
___
6. The dog climbed into the box.
___
7. The box is wrapped like a present.
___
Observe the cartoon to the right. Determine if each of the
following statements is an observation (O) or an inference (I).
8. There are doughnuts in the policeman’s car.
___
9. The 2 trucks have been damaged.
___
10. Part of the railing beside the road is missing.
___
11. The liquid on the road under the truck is blood. ___