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AQA GCSE · Question 02.6 · Organisation
Complete Figure 3. You should:
• use a suitable scale for the y-axis
• plot the data from Table 2
• draw a line of best fit.
Complete Figure 3. You should:
• use a suitable scale for the y-axis
• plot the data from Table 2
• draw a line of best fit.
How to approach this question
1. **Choose a scale:** The y-axis needs to go up to at least 100. A simple scale would be to have every 2 large squares represent 20 units (so 0, 20, 40, 60, 80, 100). Label the axis.
2. **Plot points:** For each pair of values in Table 2, find the x-coordinate (blockage %) and the y-coordinate (blood flow) and mark a small, neat cross (x) or a point in a circle (⊙) at the correct position.
3. **Draw line of best fit:** The points form a curve. Draw a single, smooth curve that goes as close as possible to all the points. Do not join the dots with straight lines.
Full Answer
The completed graph should have:
1. A linear scale on the y-axis from 0 to 100, going up in 10s or 20s. The axis must be labelled "Blood flow in cm³/minute".
2. All five points from Table 2 plotted correctly: (0, 100), (10, 64), (20, 42), (50, 8), (80, 2).
3. A smooth curve of best fit drawn through or close to the points. The curve should not be a "dot-to-dot" line.
<svg width="700" height="700" viewBox="0 0 500 500" xmlns="http://www.w3.org/2000/svg"><rect x="50" y="50" width="400" height="400" fill="none" stroke="#ccc" /><g stroke="#ccc" stroke-width="0.5"><path d="M 50 90 H 450 M 50 130 H 450 M 50 170 H 450 M 50 210 H 450 M 50 250 H 450 M 50 290 H 450 M 50 330 H 450 M 50 370 H 450 M 50 410 H 450" /><path d="M 90 50 V 450 M 130 50 V 450 M 170 50 V 450 M 210 50 V 450 M 250 50 V 450 M 290 50 V 450 M 330 50 V 450 M 370 50 V 450 M 410 50 V 450" /></g><g stroke="black" stroke-width="1"><line x1="50" y1="50" x2="50" y2="450" /><line x1="50" y1="450" x2="450" y2="450" /></g><g text-anchor="middle" font-family="Arial" font-size="12"><text x="250" y="480">Percentage (%) of coronary artery that is blocked</text><text x="20" y="250" transform="rotate(-90, 20, 250)">Blood flow in cm³/minute</text></g><g text-anchor="end" font-family="Arial" font-size="10"><text x="45" y="455">0</text><text x="45" y="370">20</text><text x="45" y="290">40</text><text x="45" y="210">60</text><text x="45" y="130">80</text><text x="45" y="50">100</text></g><g text-anchor="middle" font-family="Arial" font-size="10"><text x="50" y="465">0</text><text x="150" y="465">20</text><text x="250" y="465">40</text><text x="350" y="465">60</text><text x="450" y="465">80</text></g><path d="M 50 50 C 70 200, 150 380, 250 432 C 350 442, 430 448, 450 448" stroke="blue" stroke-width="2" fill="none" /><g fill="red"><circle cx="50" cy="50" r="3" /><circle cx="100" cy="194" r="3" /><circle cx="150" cy="282" r="3" /><circle cx="300" y="418" r="3" /><circle cx="450" y="442" r="3" /></g></svg>
To complete the graph, you must first create a suitable scale for the y-axis. The maximum value for blood flow is 100, so a scale from 0 to 100 is appropriate. A linear scale (e.g., each major grid line represents 10 or 20 cm³/minute) must be used. The axis must be labelled "Blood flow in cm³/minute".
Next, plot the five data points from Table 2 accurately. For example, for the point (10, 64), find 10 on the x-axis and 64 on your new y-axis and mark the intersection.
Finally, draw a line of best fit. Since the points do not form a straight line, a smooth curve should be drawn that passes through or very close to all the plotted points, showing the overall trend.
Common mistakes
✗ Using a non-linear scale on the y-axis.
✗ Joining the points with straight, ruled lines (dot-to-dot).
✗ Drawing a straight line of best fit when the data clearly shows a curve.
✗ Not labelling the y-axis.
Practice the full AQA GCSE Biology Higher Tier Paper 1
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