Experimental Design
What variable is purposely changed by the experimenter?
Independent
What is the purpose of a data table?
To organize measured data so patterns/relationships can be seen
Which axis normally contains the independent variable?
X-axis
What do we call repeating the same experiment several times?
Multiple trials
What does the C in CER stand for?
Claim
What is the difference between an observation and a measurement in a data table?
An observation describes what you notice; the data table records measured results
A student tests whether the amount of water given to a plant affects plant growth. The student uses 20, 40, 60, 80, and 100 mL of water and measures plant growth in centimeters. What is the independent variable, dependent variable, correct graph type, x-axis, and y-axis?
IV: Amount of water
DV: Plant growth
Graph: Scatter plot
X-axis: Water given (mL)
Y-axis: Plant growth (cm)
What variable is being measured
Dependent
Which variable should data usually be organized by?
Independent variable
Which axis normally contains the dependent variable?
Y-axis
Why do scientists perform multiple trials?
to look for patterns in the data
What does the E in CER stand for?
Evidence
In the penny-drop lab, what was measured during each trial?
The number of drops the penny held before the liquid spilled over
What are variables that are kept the same during an experiment called?
constant
What should be included with a measurement such as temperature, distance, or mass?
Units
What type of graph should be used when the independent variable is categorical, such as rock type or school subject?
How do you calculate an average?
Add all values and divide by the number of values
What does the R in CER stand for?
Reasoning
How many times was each liquid tested in the penny-drop lab?
Three trials
In an experiment testing how water temperature affects dissolving time, identify the independent variable.
Water Temp
Why should experimental data be organized from low to high values of the independent variable when possible?
It makes the relationship between the IV and DV easier to see
What type of graph should be used when both variables are numerical, such as temperature and melting time?
Scatter
Find the average of 12, 15, and 18.
15
Which part of CER should include specific numbers or observations from the experiment?
Evidence
Why should the penny be cleaned between liquids/trials?
To prevent material from a previous trial from affecting the next result
A student changes the height of a ramp and measures how far a car travels. Identify the IV and DV.
IV: ramp height; DV: car travel distance
A table has three trials for each temperature. What additional column should be added before graphing the results?
Average
Name four things a properly constructed graph should include.
Title, labeled axes with units, appropriate scale, accurately plotted data
Three trials are 39, 40, and 41 units/min. What value should usually be graphed?
the average of 40
What is the difference between evidence and reasoning?
Evidence states the data/observations; reasoning explains why that evidence supports the claim using science
Why should observations not simply repeat the numbers in the data table?
Observations provide additional sensory/qualitative information about what happened