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Scientific Investigation

The foundation of environmental fieldwork

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The Scientific Method

Environmental fieldwork uses a structured approach to collect reliable, valid data.

Your investigation must follow these steps:

Aim → Hypothesis → Plan → Collect → Analyse → Conclude

About 15–20% of exam marks come from demonstrating the scientific method correctly.

Aims & Hypotheses

Aim: A clear statement of what you intend to investigate
"To measure soil pH across the school field"

Hypothesis: A testable prediction based on scientific reasoning
"Soil near oak trees will be more acidic because leaf litter decays to produce acids"

Key difference: Aims are what you do. Hypotheses are what you predict will happen.

Types of Variables

Variable Type	Definition	Example
Independent	The variable YOU change or select	Distance from tree
Dependent	The variable you MEASURE	Soil pH value
Control	Variables you KEEP THE SAME	Soil type, season, time

Change ONE independent variable per investigation — or results become unreliable.

Sampling Strategies

Random Sampling: Every location has equal chance. Use grid + random numbers.

Systematic Sampling: Sample at regular intervals (every 5m along transect).

Stratified Sampling: Divide into zones, sample proportionally (wet/dry areas).

Choose based on habitat: Field = random. River = systematic. Varied = stratified.

Sample Size & Repeats

Repeats: Take multiple measurements at EACH location. Average them.

Replicates: Collect from MULTIPLE locations. Bigger sample = more reliable.

Minimum guideline: 10+ sample sites with 3+ repeats each = 30 data points.

Too few samples = unreliable. One anomaly skews everything.

Collecting Reliable Data

Before you start:

Calibrate equipment. Take a pilot study to check method.

During collection:

Record data immediately. Use clear tables. Include units. Note weather, time, location.

Identify anomalies: A reading very different from others. Circle it — don't delete.

Presenting Graphs

When to use each:

Line graph: Continuous data. Plot points, draw best-fit line.

Bar chart: Categories. Gaps between bars.

Scatter plot: Correlation. Show any trend.

Always label axes with units. Add a title. Include all data, even anomalies.

Analysis: Finding Patterns

Describe: "pH increases 0.5 units per metre from tree."

Calculate: Mean, median, range to compare habitats.

Use indices: Simpson's Diversity Index, species richness.

Anomalies: Equipment error? Biased sample? Real variation?

Evaluation: Reliability & Validity

Reliability: Will you get same results if you repeat? Improves with larger samples.

Validity: Are you measuring what you claim? Is method appropriate?

Evaluate: What went wrong? Sample too small? Equipment faulty? Weather changed?

Precision vs Accuracy

Precision: Readings close together. pH 6.1, 6.1, 6.2, 6.1, 6.2 = precise.

Accuracy: Close to TRUE value. Meter reading 7.5 at pH 7 = NOT accurate.

You can be precise but not accurate! This is why you calibrate instruments.

Drawing Conclusions

Refer back: Does data support or reject hypothesis?

Link to theory: Why did this happen? Connect to science concepts.

State limitations: Larger sample next time? Control for rainfall?

Use careful language: "suggests," "indicates," "supports" — not certainty.

Common Exam Mistakes

Changing multiple variables = unreliable results

Too few samples (n < 5) = weak conclusions

Graphs without axis labels or units = loses marks

Not identifying anomalies = unreliable data

Conclusions not referencing hypothesis = disconnected

Examiners expect: precise, detailed, justified scientific writing.

Fieldwork Checklist

✓ Clear aim & testable hypothesis
✓ One independent variable controlled
✓ 10+ sites, 3+ repeats
✓ Precise, calibrated equipment
✓ Data in table with units
✓ Anomalies identified, NOT deleted
✓ Graphs with proper labels
✓ Analysis describes patterns & calculates statistics
✓ Conclusion references hypothesis & theory
✓ Evaluation includes reliability & validity

Master the method, master the exam.