The Scientific Method

1. What is the Scientific Method?

The scientific method is a systematic, logical process used by scientists to investigate phenomena, solve problems, and test hypotheses using observable, measurable evidence.

Why it is important

  • Ensures results are reliable, valid, and unbiased

  • Allows experiments to be replicated

  • Forms the basis of scientific knowledge

2. Steps of the Scientific Method (In Order)

CAPS expects learners to know, explain, apply, and evaluate these steps.

Step 1: Observation

Definition: Careful noticing of a phenomenon using the senses or instruments.

  • Can be qualitative (descriptive)

  • Or quantitative (numerical)

 Example: Noticing that plants near a window grow taller than those in shade.

*Note : An observation is NOT a conclusion.

Step 2: Question / Problem Statement

Definition: A clearly stated question arising from observations that can be scientifically investigated.

Must:

  • Be specific

  • Be testable

  • Include variables

 Example: Does light intensity affect the growth rate of bean plants?

Step 3: Hypothesis

Definition (VERY IMPORTANT):

A testable prediction that explains the relationship between the independent and dependent variables.

Required:

  • Cause-and-effect format

  • If … then … because … structure (preferred)

📌 Example: If the intensity of light increases, then the growth rate of bean plants will increase because light is required for photosynthesis.

*DO NOT write a question instead of a prediction

3. Variables

3.1 Independent Variable

Definition: The factor that is deliberately changed by the researcher.

Example: Light intensity

3.2 Dependent Variable

Definition: The factor that is measured or observed as a result of the change in the independent variable.

Example: Growth rate of plants

3.3 Controlled Variables (Constants)

Definition: Factors that are kept constant to ensure that only the independent variable affects the results.

 Examples: Same plant species, Same amount of water, Same soil type, Same temperature

Possible question:  “Why must controlled variables be kept constant?”

Answer: To ensure that the results are valid and reliable.

4. Experimental Design

4.1 Aim

Definition: A clear statement of what the investigation intends to determine.

Correct wording: To investigate the effect of independent variable on dependent variable.

Example: To investigate the effect of light intensity on the growth rate of bean plants.

4.2 Apparatus / Materials

  • List all equipment used

  • Use bullet points

  • Include quantities where relevant

4.3 Method / Procedure

Definition: A step-by-step description of how the experiment is conducted.

Expectations:

  • Logical order

  • Clear steps

  • Includes control of variables

  • Written in past tense

4.4 Control Setup

Definition: A setup where the independent variable is absent, used for comparison.

 Example: Plants grown without additional light

Purpose: To provide a baseline for comparison.

5. Data Collection

5.1 Types of Data

Qualitative Data

  • Descriptive

  • No numbers

Example: Leaves appeared greener.

Quantitative Data

  • Numerical

  • Measurable

Example: Plant height = 12 cm

Use quantitative data when available.

5.2 Recording Results

Results must be presented as:

  • Tables

  • Graphs

Tables must include:

  • Title

  • Correct headings

  • Units

Graphs must include:

  • Title

  • Labeled axes

  • Correct scale

  • Independent variable on X-axis

  • Dependent variable on Y-axis

6. Analysis and Interpretation

6.1 Analysis

Definition: Examining data to identify patterns, trends, or relationships.

Correct phrasing:

  • Increases

  • Decreases

  • Remains constant

6.2 Interpretation

Definition: Explaining what the results mean using biological knowledge.

Example: Increased light intensity led to faster growth because it increased the rate of photosynthesis.

7. Conclusion

Definition: A statement that accepts or rejects the hypothesis based on results.

General rule:

  • Must refer back to the aim and hypothesis

  • No new information

Example: The hypothesis is supported as plants exposed to higher light intensity showed increased growth.

8. Reliability, Validity, and Accuracy

8.1 Reliability

Definition: The extent to which results are consistent and repeatable.

Improved by:

  • Repeating experiments

  • Large sample size

8.2 Validity

Definition: Whether the investigation tests what it intends to test.

đź“Ś Improved by:

  • Controlling variables

  • Using a control setup

8.3 Accuracy

Definition: How close measurements are to the true value.

Improved by:

  • Using precise instruments

9. Sources of Error

Random Errors

  • Unpredictable

  • Reduced by repetition

Systematic Errors

  • Consistent bias

  • Caused by faulty equipment

10. Ethical Considerations (Grade 12 Focus)

Consider ethics when:

  • Using animals

  • Using humans

  • Using the environment

Principles:

  • No unnecessary harm

  • Informed consent

  • Humane treatment

11. Common Exam Mistakes 

  • Confusing variables

  • Writing vague hypotheses

  • Missing units on graphs

  • Conclusions not linked to hypothesis

  • Forgetting control variables

12. Good phrases to use

  • “to ensure validity and reliability”

  • “a testable prediction”

  • “deliberately changed variable”

  • “measured response”

  • “baseline for comparison”