Data Analysis, Interpretation & Statistics
Analysing patterns, calculating statistics, and explaining results using geographical theory
Analysis = WHAT
Describing patterns in data - what the numbers/graphs show
"River width increased from 2m to 12m"
Interpretation = WHY
Explaining WHY patterns occur - link to geographical theory/processes
"...due to tributary inputs increasing discharge, as Bradshaw model predicts"
Statistical Techniques
Mean (Average)
Sum of all values ÷ Number of values
Use: Compare typical values between sites
Limitation: Affected by outliers (extreme values)
Median
Middle value when data is ordered
Use: When data has outliers (less affected than mean)
Advantage: Not skewed by extreme values
Mode
Most common/frequent value
Use: Categorical data, identifying typical value
Limitation: May be no mode or multiple modes
Range
Maximum value - Minimum value
Use: Compare variation/spread between sites
Large range = high variability, small range = consistent
Interquartile Range (IQR)
Q3 - Q1 (range of middle 50%)
Use: Better than range if outliers present
Advantage: Removes extreme outliers from calculation
Percentage Change
((New - Old) ÷ Old) × 100
Use: Comparing change over time or distance
Shows proportional change, not just absolute difference
Practice calculating mean, median, mode, range, and percentage change
Mean
Sum of all values ÷ Number of values
Pebble sizes (cm): 5, 8, 6, 7, 9
Describing Data from Graphs
Line Graphs - Describing Trends
- • Overall trend: "Generally increasing/decreasing/stable"
- • Specific changes: Quantify with numbers ("increased from 2m to 12m")
- • Rate of change: Where is change fastest/slowest?
- • Anomalies: Any values that don't fit the pattern?
Bar Charts - Describing Patterns
- • Comparisons: Use multipliers ("3.75× higher")
- • Similarities/differences: Group similar values
- • Categories: Rank from highest to lowest
Scatter Graphs - Describing Relationships
- • Correlation type: Positive, negative, or none
- • Strength: Strong (close to line), weak (scattered), moderate
- • Anomalies: Points far from line of best fit
- • r value: Quote if given (±0.7-1.0 = strong)
Learn to write strong analytical descriptions of graphs and data
River width increases from 2m at Site 1 (source) to 12m at Site 6 (mouth) over 10km distance.
Which description best analyses this trend?
Interpreting Data (Linking to Theory)
Interpretation means explaining WHY patterns occur by linking to geographical theory:
Quote specific data: "15m movement", "decreased from 12cm to 3cm"
Reference theory: "Bradshaw model predicts...", "Urban decline cycle suggests..."
Link cause and effect: "BECAUSE attrition erodes particles, THEREFORE size decreases"
Consider alternatives: "However, human management may also affect..."
Build interpretations by linking analysis to theory and processes
Analysis (WHAT):
Bedload size decreased from 12cm mean at Site 1 to 3cm at Site 6
Step 1: Which geographical theory does this relate to?
Question: "Analyse the data shown in Figure X (graph showing river width increasing from 2m to 12m over 10km distance)." (4 marks)
Weak Answer
1-2/4 marks"The river gets wider as you go downstream. It starts at 2m and ends at 12m. This is what happens to rivers."
Why weak:
Strong Answer
4/4 marks"River width increases progressively from 2m at the source to 12m at 10km downstream, a 500% increase. The rate of widening is greatest in the first 4km (2m to 8m = 6m increase), then slows in the lower course (8m to 12m = only 4m increase over remaining 6km). This supports Bradshaw model which predicts channel width increases downstream as discharge rises due to tributary inputs adding water. The faster widening in upper/middle course corresponds to where the OS map shows major tributary confluences at 2km and 5km, explaining the steepest increases at those points."
Why strong:
Limitations & Evaluation
• Sample size: Too small to be representative
• Timing: Only one time of day/year
• Location bias: Only sampled certain areas
• Weather: Conditions affected results
• Subjectivity: Personal opinion varies
• Equipment precision: Limited accuracy
• Human error: Inconsistent measurements
• External factors: Uncontrolled variables
• Method limitations: Technique doesn't capture true value
Identify limitations and suggest improvements for fieldwork methods
Questionnaire Survey
20 questionnaires completed at shopping center, 2pm on a Tuesday
Click to reveal limitations (try to think of them first!):
• Quantify: Use specific numbers, not vague terms
• Calculate: Mean, %, range shows data processing
• Identify anomalies: Note + explain outliers
• Link sources: Primary data + secondary evidence
• Name theories: Bradshaw, bid-rent, etc.
• Evaluate critically: Acknowledge limitations
Question 1 of 5 | Score: 0
What is the difference between analysis and interpretation?
Analyse the data shown in Figure X (graph showing pebble size decreasing from 12cm to 3cm mean over 6 sites downstream). (4 marks)