Class 7 Maths Chapter 13 Connecting the Dots... Visual Infographic | NCF 2023 Ganita Prakash
Chapter 5: Connecting the Dots...
Statistical Thinking, Measures of Central Tendency, Data Visualisation & Graph Analytics
📊 Statistical Thinking
Questions answered by collecting data that anticipates variability (e.g. "How tall are Grade 7 students?").
Displays data points along a scaled number line to immediately reveal clustering, spread, and gaps.
Extreme values that deviate significantly from the rest of the dataset and strongly pull the mean.
⚖️ Measures of Central Tendency
1. Arithmetic Mean (Fair-Share):
Mean = (Sum of all values) / (Total number of values). Represents the balanced, equalised share across all members.
2. Median (Middle Position):
The exact middle value in ordered (sorted) data. If n is even, take the mean of the two middle values. Highly resistant to outliers!
3. Mean vs. Median Skew:
• High outlier → Mean > Median
• Low outlier → Mean < Median
• Balanced data → Mean ≈ Median
🏛️ Heritage & Graphical Tools
Brahmagupta (628 CE) used Samarajju, Mahavira (850 CE) used Samikarana, and Bhaskara II (1150 CE) defined mean as Samamiti (equal measure).
Places two or more related bars side-by-side on the same scale for direct, multidimensional comparison.
A 16-foot rod was measured from 16 men standing toe-to-heel and divided into 16 parts to standardize 1 standard foot!
🔍 2-Step Framework for Reading Graphs & Case Studies
• Step 1 (Identify What is Given): Examine graph layout, axis labels, specific unit scale (e.g. 1 unit = 20 rockets or 5 hours), and legends.
• Step 2 (Infer & Interpret): Spot maximums, minimums, growth trends over time, and proportional comparisons between categories.
• Global Sunlight Inversion: Clustered bars show peak daylight in June for Helsinki, Finland (Northern Hemisphere) vs. December for Wellington, New Zealand (Southern Hemisphere).
• Zero Score vs. Missing Match: Scoring 0 counts as an innings (included in denominator n); missing a match is omitted from the match count completely!
⚠️ Common Statistical Traps
Trap 1: Forgetting to Sort for Median
You CANNOT pick the middle number from raw data! Data must be strictly arranged in ascending order first before finding the median.
Trap 2: Using Mean When Outliers Dominate
A team score of 407/10 can have a median score of 0 if 6 out of 11 players score ducks! In skewed data, the median represents typical performance far better than the mean.
