Variables Practice
Define the four types of variables and what a hypothesis is below:
Independent Variable (IV) – the variable the scientist changes
Dependent Variable (DV) – the result, what is measured
Controlled Variable (CV) – variables that are kept the same in the
experiment, cannot be IV or DV
Uncontrolled Variable (UV) – errors, cannot be IV or DV
Hypothesis – educated guess to the purpose question, MUST
contain the IV, DV and “because”
Using the purposes given below – list the IV, DV, and write an
hypothesis (IV, DV, because).
1. How does the speed of a ping pong ball affect how long it stays in the
air?
IV – speed of ping pong ball (faster/slower)
DV- how long ping pong ball stays in the air (longer/shorter)
Hypothesis –
If the speed of the ping pong ball is faster/slower, it will stay
longer/shorter in the air because….
2. When classical music is played to a group of toddlers, how relaxed
does their heart rate become?
IV – Classical music (softer/louder)
DV- heart rate (faster/slower)
Hypothesis When soft/loud classical music is played, the heart rate will be
faster/slower because….
3. Does heating a cup of water allow it to dissolve more sugar?
IV – temp of water (hotter/less hot)
DV- amount of sugar dissolved (more/less)
Hypothesis –
When the water is at a hotter/less hot temperature, more/less sugar will
dissolve because…..
4. Does increasing the amount of batteries in a circuit increase the
power output?
IV – amount of batteries (more/less)
DV- power output (higher/lower)
Hypothesis When there is are more/less batteries in a circuit, the power output will
be higher/lower because…..
In the next section, based on the purpose given, list the IV, DV,
three CVs and three UVs.
1. Does the increase in fertilizer cause pine trees to grow taller?
IV – fertilizer amount (more/less)
DV- height of pine trees (taller/shorter)
CVs – same scientist, same environment, same type of tree, same
water amount, same light amount, same soil, same pot planted in, same
temperature of area, same ruler to measure with
UVs – weather, bug infestation, lightning strike, inaccurate
measuring with ruler, scientist forgets to water, tree gets sick
2. Who will run the 50m dash faster, a kindergartener, an 8th grader or a
12th grader?
IV – age of runner (younger/older)
DV- time it takes to run 50m (faster/slower)
CVs – same scientist, same environment, same track type, same
stop watch, same day of race, same race
UVs – mood of runners (hungry, tired, bored, excited), stopwatch
not started/stopped at exact moment, stopwatch breaks, freak storm
hits, runner trips
3. How does the surface of a road affect the stopping ability of a
Ferrari going 70 kmph?
IV – surface of road (smoother/rougher)
DV- stopping ability of Ferrari (faster/slower)
CVs – same scientist, same environment, same car, same driver,
same tape measure, same stopwatch
UVs – driver has heart attack, car’s tire pops, engine stops working,
stopwatch not started/stopped at exact moment, tape measure used
inaccurately, road deteriorates, weather (temp, wind, rain, etc)
4. Does the amount of sleep a middle schooler gets at night affect their
ability on a math test?
IV – amount of sleep (more/less)
DV- math ability (better/worse)
CVs – same scientist, same environment, same aged student, same
math skill level, same meals, same test
UVs – mood of students, bad night’s sleep – nightmares, waking up;
test problems – copying, missed a page; pencil breaks
5. Can a mouse be trained to run through a maze in under three minutes?
IV – trained mouse (trained/untrained)
DV- time through maze (better/worse)
CVs – same scientist, same environment, same mouse, same maze,
same stopwatch, same training methods, same trainer, same reward
UVs – stopwatch stops working, stopwatch not started/stopped
exactly, mood of mouse, if mouse gets sick or dies, maze collapses