Scientific Method & Experimental Design Problem/Purpose Hypothesis Experiment Controls Variables Constants Materials Procedure Data and Observations Analysis Conclusion Theory

Do plants need food to grow? Problem/Purpose Do plants need food to grow? Identify what it is you want to investigate, usually based on something you’ve observed.

Hypothesis what you think will happen If a plant is given more food, then it will grow taller than if it is given no food at all what you think will happen a testable explanation for an observation often given in the “If…… then…..” format

Experiment the controlled test of a hypothesis contains: constants control group variables

Experiment Sayda wanted to test the effects of different kinds of fertilizer (food supplement) on plant growth. She created an experiment using 4 plant setups, each containing 5 plants. All plants are the same kind and age, and they have all been planted in 1 kilogram of the same potting soil. Each plant in every group is given 500 milliliters of water daily and exposed to 8 hours of sunlight. Group 1 is given 10 grams of plant fertilizer Group 2 is given 5 grams of plant fertilizer Group 3 is given 20 grams of fertilizer Group 4 is given no fertilizer at all. The height in centimeters of each plant is measured and recorded every 5 days.

Experiment Now, write out in words what you think is going to happen by finishing the statement started for you. If plants are given _____________ fertilizer, then after 15 days they will be _________________ than plants receiving different amounts of fertilizer. Suggested answer: If plants are given more fertilizer, then after 15 days they will be taller than plants receiving less fertilizer.

Experiment Set-up of controlled experiment: Group 1 Group 2 Group 3

Experiment The results after 15 days: Group 1 Group 4 Group 2 Group 3

Experiment constants- things that are the same for all groups What were the constants in Sayda’s experiment? Suggested answer: “All plants are the same kind and age, and they have all been planted in 1 kilogram of the same potting soil. Each plant in every group is given 500 milliliters of water daily and exposed to 8 hours of sunlight.”

Experiment control group Suggested answer: serves as a standard of comparison contains all constants but not the variable the group you don’t change from the natural condition What was the control group in Sayda’s experiment? Suggested answer: “Group 4 is given no fertilizer at all.”

Experiment variables This word comes from the word “vary”, which means change or different. For example, you could say the colors in the flowers vary from bright red to pale yellow.

Experiment dependent variable- what the scientist or experimenter is testing for/measuring; what is observed and recorded goes on Y axis independent variable- what the scientist or experimenter changes in the experiment goes on the X axis

Experiment

Experiment What was Sayda measuring/testing for in the experiment? that is the dependent variable What was Sayda manipulating/changing in the experiment? that is the independent variable Suggested answer: dependent variable = height in centimeters independent variable = amount of fertilizer

Materials and Procedure materials- what you use to conduct the experiment What are the materials used in Sayda’s plant experiment? Suggested answer: 20 plants 20 pots 20 kg potting soil tap water (500 mL per plant per day) source of sunlight metric ruler 175 grams fertilizer electronic balance

Materials and Procedure procedure- a logical order of steps to follow in solving the problem often listed as numbered steps.

Data and Observation what happened during the experiment involves all 5 senses (when safe to touch, taste or smell), otherwise we rely on sight and sound can be qualitative- observations that are not measured Examples: color, smell, taste, texture can be quantitative- observations that are measured Examples: temperature, mass, height, volume

Data and Observation includes the results in the form of data data should be included as charts, tables and graphs make sure all data tables have a title and axes are descriptively labeled Table 1. The effect of the independent variable on the dependent variable Independent variable (x) Dependent variable (y)

Analysis the part of an experiment where you decide what the data means (comes from the word analyze) graphs are one tool used to analyze data

Analysis Graphing Guidelines: Include a title indicating variables (what exactly does this chart show the reader). Label the X and Y axis including units. DRY- Dependent/Responding variable on Y-axis MIX- Manipulated/Independent variable X-axis

Amount of fertilizer (g) Graph 1. The Effect of Fertilizer Amount on Plant Height Group 1 Group 2 Group 3 Group 4 O in. 2 in. 4 in. 6 in. 8 in. 10 in. 12 in. 14 in. Plant growth (cm) Amount of fertilizer (g)

Conclusion addresses the hypothesis shows that the data supports or disproves your hypothesis makes a clear relationship between the problem and results

Theory theory- unifying explanation for a broad range of observations in everyday use, we say “theory” when we mean we are guessing what happened or why something happened IN SCIENCE, theories are “the facts as we know them”; know scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers; scientific theories are well-established and highly-reliable explanations

                      Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they’re supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks. Group B made 2,113 stacks. Identify the: Control Group Independent Variable Dependent Variable What should Smithers' conclusion be? How could this experiment be improved?

Suggested answers: Identify the: Control Group Group B - water Independent Variable type of drink Dependent Variable number of stapled sets of papers What should Smithers’ conclusion be? The special juice slows down, not speeds up, works when stapling papers How could this experiment be improved? * same breakfast & lunch *regulate the amount of caffeine *measure the amount of juice *count stapling rate before the juice for both groups and do a percent increase

                      Homer notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower with coconut juice. He sprays the other half of the shower with water. After 3 days of “treatment” there is no change in the appear- ance of the green slime on either side of the shower.   What was the initial observation? Identify the- Control Group Independent Variable Dependent Variable What should Homer's conclusion be?

Suggested answers: What was the initial observation? Green slime in the shower Identify the: Control Group half sprayed with water Independent Variable type of cleaning solution Dependent Variable amount of green slime “killed” What should Homer’s conclusion be? Coconut juice does not work to remove green slime