1. Happy Friday Scientists!
DQ:
Identify the IV, DV and constants in the following scenario: A study was done to find if fuel types affect the engine’s performance in a car.
Today:
Review Density Lab
What are the different types of data and which type of graph should we use for each? (study guide)
Data and Graph Types Practice
Review IV/DV/Constants
HW:
Return work and discuss grades L4

2. Variables and Constants
Variable – Any factor that can change in a scientific investigation or experiment

3. Types of Variables Independent Dependent
What the scientist chooses or changes
Known before starting the experiment.
The factor that is intentionally changed by the investigator in an experiment
There can be only one independent variable in an experiment
The factor that you measure or observe as data
The factor that will change as a result of the independent variable
This variable depends on the independent variable.
There can be one or more dependent variables in an experiment

4. Constants Sometimes called controlled variables
The factors or conditions that are kept the same (unchanged) in an experiment
There are many controlled variables in an experiment.

5. Graphing Study Guide
Are you ready to go?
Complete the handout!

6. There are 4 major types of graphs we’ll use this year.
I can remember that

7. Types of Data
Discrete data = consist of categories (days of the week, kind of animal, color)
Continuous data = consist of measurements involving a scale with equal measurements; a range of values (temperature, length of time in hours, height in centimeters)

8. Four major types of graphing
Pie chart/graph = consist of categories (display percentages)
Bar graph = used to represent discrete data; the IV is typically qualitative and DV is typically quantitative

9. Four major types of graphing
3. Line graph = used to represent continuous data, usually tracking changes over time; the IV and DV are both quantitative and the line connecting the points has meaning 4. Scatter plot = similar to a line graph, but the data points are NOT connected because a connecting line would have no meaning; a line of best fit might be constructed to show a trend in the data; IV and DV are typically both quantitative

10. Scatter plot
This is a line of best fit – it is a straight line that comes as close to possible as all the data points
The data points should NOT be directly connected because the IV is discrete

11. Bar Graph
This is what we mean by discrete data – it’s a category and there’s no “middle value” between each category

12. Line Graph
Each value here has meaning (I could determine Jill’s elevation at 3.2 hours) so I connect my data points with a line

13. Pie chart
Here I have data organized in a percentage out of 100 – this is good way to represent it

14. A few final thoughts
Scientists must represent their data graphically in a fair way that tells the most accurate story
It is possible to change the scale of a graph to make it look like the data tells a much different story than the numbers actually show
Additional labels might also be used to make the reader infer certain things from the same set of data

15. For example…
At most, how different is the average rainfall from this year’s rainfall?
This graph has been manipulated to make it look like there is a much bigger difference in rainfall than 0.4 cm
Bad scientist!

16. A more accurate graph
Good scientist!

17. Another Example What conclusions can you draw from this graph?
U.S. Jobs by Quarter
Number of jobs (thousands)
Quarter, Year
Image source:

18. Here’s the same graph with a few extra labels…
The data is the same but it could be used to create different inferences
Image source:

19. Examples
What is the scientist changing? (independent variable)
The temperature of the ball
What is the scientist measuring? (dependent variable)
Bounce height of the ball when dropped
What should be kept the same or constant for a fair test? (constants)
Same ball
Dropped from same height
Onto same surface.
Etc.
Question: Does changing the temperature of a ball affect the height the ball will bounce?

20. Question: Does changing the color of light change the growth rate of plants?
Independent?
Color of light
Dependent?
Growth rate of plants
Constants?
Age of plant
Type of plant
Amount of light
Amount of water
When measured
Type of container
Etc.