Scientific Method

The scientific method is oh-so-amazing and crucial to the majority of scientific breakthroughs in last four centuries. Some discoveries are stumbled upon through observation, but only through conducting controlled experiments are these observations tested and confirmed. When conducting an experiment it is important to have a hypothesis for what you believe the results will be. “A hypothesis is the obligatory starting point of all experimental reasoning. Without it no investigation would be possible, and one would learn nothing: one could only pile up barren observations. To experiment without a preconceived idea is to wander aimlessly.”

Hypothesis: An educated guess for the results of an experiment.

Once you have a clear and testable hypothesis, you need to design your experiment. Let’s use an example. Stan has been conducting an experiment while preparing for the school year. This year all of the elementary classrooms will have plants growing in hydroponic growth tanks (aerogarden). Stan has never done this before, so he wanted to figure out what nutrients will help with growth. Each hydroponic garden comes with a bottle of plant food, but he wants to see if he can grow them even faster. He does some research and decides that adding potassium or phosphorous might help plant growth.

Ok, this is the part of Stan’s experimental design where he could make a BIG mistake. He could decide that he will just add the included plant food AND potassium to one garden. The other garden would receive plant food AND phosphorous. He will let them grow and see which grew fastest. BIG MISTAKE. If he observes that the garden with phosphorous grew faster, he might conclude that this is how he should grow all of his hydroponic gardens. What’s missing? There was no CONTROL.

Control: An experimental group used as a standard to compare to the other experimental groups in which one independent variable is changed.

It is absolutely possible that adding phosphorous or potassium is actually BAD for the growth of these hydroponic gardens. Maybe these nutrients are already in the food, and extra only slows growth. Stan would never know that because he didn’t have a CONTROL a garden where only the plant food was used.

Ok, lets fix his experiment. He now has 3 experimental groups. Group 1 is the control where only the included plant food is used. Group 2 is plant food + potassium. Group 3 is plant food + phosphorous. This is a much better experimental design, but we need to dig a little deeper. The potassium and phosphorous are what scientists call INDEPENDENT VARIABLES. The only thing we want to test are the effects of these two nutrients compared to the control.

Independent Variables: The one condition that is changed during an experiment while other conditions remain the same.

In order for the results of this experiment to be convincing each hydroponic garden will need receive the exact same amount of plant food, added nutrients(potassium/phosphorous), same grow bulbs, same location, and same exact species of plant. All of these variables that we keep the same are called CONTROLLED VARIABLES.

Controlled Variables: The elements of an experiment that are NOT changed between different experimental conditions.

The need for these variables is pretty obvious. If stan chose to use three different species of plants for each garden, then how could he compare their growth? Different plants grow at different rates. If he used different grow bulbs, then any difference in growth might be due to the strength of the bulbs.

Once stan has his experiment designed, he needs to decide how he is going to know if his hypothesis was correct. He needs to know beforehand how he will measure growth. This is called the DEPENDENT VARIABLE in an experiment. Stan could use height of the plants, number of leaves or both as his dependent variables.

Dependent Variable: The variable that is measured or observed.

Now Stan can conduct his experiment. He is actually doing this right now, but his results are not in yet. Let’s pretend that after growing mini-Jalepeno plants for 3 weeks in 3 separate hydroponic tanks(Group 1,2,3) Stan observes that the control plants grew the tallest, while the potassium and phosphorous groups grew the slowest. Stan would then conclude that adding additional potassium or phosphorous is not beneficial to growth. Stan would then decide to start all of his hydroponic gardens with the plant food provided in each kit, and not add additional nutrients.

Conclusion: A judgement or decision based on the results of an experiment.

Ok… Now that you’re a scientific method wizz, let’s test your knowledge. For the following experiments, you need to determine the parts of an experiment listed below.

N40 AB.CDE W105 FG.HJK

Independent Variable = 0

Dependent Variable = 3

Control Group = 5

Controlled Variables = 4

Hypothesis = 1

Conclusion = 7

Experiment #1: Dr. P goes to a breeder and buys 14 goldendoodle puppies. That’s right! These adorable hypoallergenic fluff-monsters are part of a ridiculous experiment. He first separates the dogs into two groups, 7 in each group. He separates the dogs and labels one Group A and the other Group B. He wants to test his hypothesis that dogs will respond quickly to common demands like sit/stay/roll-over when they are given instant rewards.

In Group A he lets the dogs run around a large fenced area, periodically giving them liver-snap treats at random every day. He also tries to teach the dogs common behaviors like sit,stay, and roll-over for 30 minutes a day. Treats are NOT given out during the training. Group B dogs have the same sized fenced area, receive the same liver-snap treats, but only during the 30 minutes of training. After telling the group of 7 dogs to “Sit” he gives a treat to each dog who sits, and so on. After 2 weeks of this experiment Dr. P test which group of dogs responds to commands more often, and the speed at which they respond. Not surprisingly, the dogs who received treats during training responded faster to commands.

A = The same breed of dog. The same size enclosure. The same liver-snap reward. The same amount of time training. The same litter of dogs. Etc. (Subtract number by 4)

B = The number of dogs that were given a second type of treat.

C = The dogs in Group A

D = “Giving dogs treats during training improved the speed and response to commands.”

E = The speed and accuracy of dog commands at the end of the experiment. (Subtract this number by 3)

Experiment #2: When Stan was a kid he famously jumped off the roof of his 2 story house in order to fly. His sister had convinced him that “If you believe hard enough” he could do it. As it turns out, the only thing he could do was destroy an aluminum garden shed and cry a bunch. Now imagine little Stan designed his experiment first. He would first choose some groups to test. Group A would be a control where Stan jumps off the roof and a friend times how long it takes for him to reach the ground. In Group B Stan would attempt to believe REALLY HARD that he could fly before jumping, and in group 3 he could use a sheet to try and slow his fall.

F = “Jumping with a sheet will slow Stan’s rate of falling the most.”

G = The amount of time it takes for Stan to reach the ground after jumping from the roof.

H = Jumping off the roof without believing “really hard” or using a sheet. Just a jump.

J = “Stan fell from the roof at the same speed no matter what the conditions were. There was no effect of believing “really hard” that he could fly.” (Subtract number by 4)

K = Stan always jumped from the same height, measured with the same stopwatch, jumped at the same angle, etc.

You can check your answers for this puzzle on GeoChecker.com.

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