topic 11.2: measurement and data processing graphing
TRANSCRIPT
Topic 11.2: Measurement and Data Processing
Graphing
11.2 Graphing
EI: Graphs are a visual representation of trends in data.
NOS: The idea of correlation – can be tested in experiments whose results can be displayed graphically.
U 1. Graphical Techniques
Why do are graphs used?
•Graphs are an effective means of communicating the effect of the independent variable on a dependent variable, and can lead to determination of physical quantities.
U1. Graphical Techniques
• Graphs are used to present and analyze data.– show the relationship
between the independent variable and the dependent variable
Independent
Example Graph
U2. Sketched graphs
• Sketched graphs:– Have labeled, but unscaled
axes– Used to show qualitative
trends• Variables that are
proportional or inversely proportional
Independent
Example Graph
U3. Drawn Graphs
Graphs MUST have:• A title• Label axes with
quantities and units
Time (min.)
Candle Mass After Burning
U3, A &S 1. Drawn Graphs
Graphs MUST have:• Use available space as
effectively as possible• Use sensible linear
scales- NO uneven jumps• Plot ALL points correctly
Time (min.)
Candle Mass After Burning
A&S 3. Best Fit Lines
Best Fit Lines should be – drawn smoothly and
clearly– Do not have to go
through all the points, but do show the overall trend
Time (sec)
A & S 4 Physical quantities from graphs
• Find the gradient (slope) and the intercept• Use y = m x + b for a straight line
• y= dependent variable• x = independent variable• m= the gradient (slope)• b = the intercept on the vertical (y) axis
A & S 4 Physical quantities from graphs
• Ex: to find the slope (m), find 2 data points (2,5) and (4, 10)
m= (y2-y1) = (10-5) = 5 = 2.5
(x2-x1) (4-2) 2
A & S 2. Interpretation of Graphs
Variables:Independent- the cause,
plotted on the horizontal axis (x-axis)AKA: Manipulated
Independent
Example Graph
A & S 2 Interpretation of Graphs
Variables:Dependent- the effect,
plotted on the the vertical axis (y-axis)AKA: Responding
Independent
Example Graph
A & S 2. Interpretation of Graphs
Interpolation: determining an unknown value using data points within the values already measured
A & S 2. Interpretation of Graphs
Extrapolation: when a line has to be extended beyond the range of the measurements of the graph to determine other values– Absolute zero can be
found by extrapolating the line to lower temperatures.
Graphing in Excel
• Enter data into Excel– IV in left column– DV in right column
• Highlight data with mouse• Click on
– “Insert” tab– “Scatter with smooth lines & markers”
Graphing in Excel• Edit titles under “Chart Tools: Layout”
– Graph Title: “IV vs. DV”– IV with units on x-axis– DV with units on y-axis– Change gridlines to your liking
• Establish Line of Best Fit– Right click on line and “Add Trendline”– Make sure “Linear,” “Automatic” and “Display Equation
on Chart” are all checked– Press Close… and voila!!!