Visualizing Data Relationships Through Scatter Diagrams

Contents 4. Scatter diagram and best fit line 5. Pie chart 6. Triangular graph

4. Scatter diagram and best fit line A scatter diagram uses points to show the distribution pattern of variables The X-axis represents the independent variable The Y-axis represents the dependent variable We can add a best fit among the scatter points to determine the direction and strength of relationship between the variables Contents Contents

4. Scatter diagram and best fit line Drawing steps: Monthly mean temperatures and monthly mean vapour pressures of City A Month Jan Feb Mar Apr May Jun Mean vapour pressure (hPa) Mean temperature (oC) 14 16 18 23 28 31 19 19 21 25 28 30 Month Jul Aug Sep Oct Nov Dec Mean vapour pressure (hPa) Mean temperature (oC) 32 32 29 24 19 15 31 31 30 28 24 20 Contents Contents

4. Scatter diagram and best fit line Draw the X-axis, and then label the unit Monthly mean temperature (oC) and values. Contents Contents

4. Scatter diagram and best fit line Draw the Y-axis, and then label the unit Monthly mean vapour pressure (hPa) and values. Contents Contents

4. Scatter diagram and best fit line Take January as an example. Plot a scatter point at the interaction of 19oC on the X-axis and 14hPa on the Y-axis. Contents Contents

4. Scatter diagram and best fit line Repeat Step 3 to plot the scatter points of other months. Contents Contents

4. Scatter diagram and best fit line Add a best fit line among the scatter points (ensure that there are roughly the same number of scatter points on both sides of the best fit line). Contents Contents

4. Scatter diagram and best fit line Add a title. Contents Contents

5. Pie chart It presents the percentages of different items in the population Drawing steps: Commuting methods used by Secondary 6 students Commuting method Number of students Bus 32 MTR 28 Minibus 11 Walking 46 Others 3 Total 120 Contents Contents

5. Pie chart Convert the data into percentages. Take Bus as an example: (32 120) 100% = 27% Convert the percentages into angles of sectors. Take Bus as an example: 360o 27% = 97% Commuting methods used by Secondary 6 students Commuting method students Number of Percentage Angle of sector 97o Bus 32 27% 83 32 137 11 360 MTR 28 23% Minibus 11 9% Walking 46 38% Others 3 3% Total 120 100% Contents Contents

5. Pie chart Use a protractor to draw the sectors. Contents Contents

5. Pie chart Fill the sectors with different colours or patterns, and then label them. Contents Contents

5. Pie chart Add a title. Contents Contents

6. Triangular graph It is used for comparing geographical phenomena composed of three items E.g. compositions of different soil samples Drawing steps: Compositions of Soil Samples A and B Composition (%) Soil sample Clay Silt Sand A 93 6 1 B 7 22 71 Contents Contents

6. Triangular graph Draw an equilateral triangle (with interior angles of 60o). Label Clay (%) , Silt (%) and Sand (%) on the axes. Contents Contents

6. Triangular graph Divide each axis into ten equal parts, and label 0 to 100. Contents Contents

6. Triangular graph For each axis, draw lines that are parallel to the other two axes. Ensure that there are three lines passing each intersection. Contents Contents

6. Triangular graph According to the composition percentages of clay (93%), silt (6%) and sand (1%) of Soil Sample A, mark the intersection in the graph to represent the composition of Soil Sample A. Contents Contents

6. Triangular graph Repeat Step 4 to mark the composition of Soil Sample B. Add a title. Contents Contents

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