Experimental Design Experimental Design and Scienceand Science

Designing an Experiment

Can you name the 6 concepts of experimental design?

Can you name the 6 concepts of experimental design?

independent variableindependent variable

dependent variabledependent variable

constantsconstants

control groupcontrol group

experimental groupexperimental group

repeated trialsrepeated trials

Experimental DesignExperimental Design

You will be divided into lab table groups Each table will analyze a different

experiment for the design parts. Use the form in front of you to answer all

the questions.

Experimental Design DiagramExperimental Design DiagramTitle: The effect of ...IV... on ...DV...

Hypothesis: If the ...IV... is modified in this way,then this will happen to the ...DV...

Independent variable:

these boxesshow how theIV is modified

_____trials _____trials _____trials _____trials _____trials

Dependent Variable:

Constants:

Control:

Scenario 1: Compost and Bean PlantsScenario 1: Compost and Bean Plants

After studying about recycling, members of Jessica's biology class investigated the effect of various recycled products on plant growth. Jessica's lab group compared the effect of different aged grass compost on bean plants. Because decomposition is necessary for release of nutrients, the group hypothesized that older grass compost would produce taller bean plants Three flats of bean plants (25 plants/flat) were grown for 5 days. The plants were then fertilized as follows: (a) Flat A: 450 g of three-month-old compost, (b) Flat B: 450 g of six-month-old compost, and (c) Flat C: 0 g compost. The plants received the same amount of sunlight and water each day At the end of 30 days the group recorded the height of the plants (cm).

Experimental Design DiagramExperimental Design DiagramTitle: The effect of different aged compost on beanplant growth.

Hypothesis: If older compost is applied, then plantgrowth will be increased.

Independent variable: Age of Compost

these boxesshow how theIV is modified

3 month oldcompost

6 month oldcompost No compost

# trials 25 trials 25 trials 25 trials

Dependent Variable: Height of plants (cm)

Constants: amount of light, water, compost

Control: no compost

Scenario 2 Metals & Rusting Iron Scenario 2 Metals & Rusting Iron

In chemistry class, Erza determined the effectiveness of various metals in releasing hydrogen gas from hydrochloric acid. Several weeks later, Ezra read that a utilities company was burying lead next to iron pipes to prevent rusting Ezra hypothesized that less rusting would occur with the more active metals. He placed the following into separate beakers of water: (a) 1 iron nail, (b) 1 iron nail wrapped with an aluminum strip, (c) 1 iron nail wrapped with a magnesium strip, (d) 1 iron nail wrapped with a lead strip. He used the same amount of water, equal amounts (mass) of the metals and the same type of iron nails. At the end of 5 days, he rated the amount of rusting as small, moderate, or large. He also recorded the color of the water.

Experimental Design DiagramExperimental Design DiagramTitle: The effectiveness of various metals in preventing the rusting of iron.

Hypothesis: I f the chemical activity of the metallic wrapper is increased, then less rusting of iron will occur.

Independent variable: Type of metal wrapping strip these boxes show how the IV is modified

Iron nail with no metal

Iron nail with magnesium

Iron nail with aluminum

Iron nail with lead

# trials 1 trial 1 trial 1 trial 1 trial

Dependent Variable: amount of rusting , color of water

Constants: amount of water, mass of metal, type of nail

Control: nail with no metal

Perfumes & Bee's BehaviorPerfumes & Bee's Behavior

Evelyn read that certain perfume esters would agitate bees. Because perfume formulas are secret, she decided to determine if the unknown Ester X was present in four different perfumes by observing the bees' behavior. She placed a saucer containing 10 ml of the first perfume 3 m from the hive. She recorded the time required for the bees to emerge and made observations on their behavior. After a 30-minute recovery period, she tested the second, third, and fourth perfumes. All experiments were conducted on the same day when the weather conditions were similar, e.g., air, temperature and wind.

Experimental Design DiagramExperimental Design DiagramTitle: The effect of various perfumes on the behavior of bees.

Hypothesis: I f the perfume contains Ester X, then the bees will display agitated behavior.

Independent variable: Type of perfume these boxes show how the IV is modified

Perfume 1 Perfume 2 Perfume 3 Perfume 4

# trials 1 trial 1 trial 1 trial 1 trial

Dependent Variable: time to emerge , behavior of bees

Constants: amount of perfume, weather, distance from hive

Control:

Fossils and Cliff DepthFossils and Cliff Depth

Kenzie observed that different kinds and amounts of fossils were preset in a cliff behind her house. She wondered why changes in fossils content occurred from the top to the bank. She marked the bank at five positions: 5,10,15, 20, and 25m from the surface. She removed 1 bucket of soil from each of the positions and determined the kind and number of fossils in each sample.

Experimental Design DiagramExperimental Design Diagram

Title: The effect of depth on the different types and amounts of fossils.

Hypothesis: If depth increases in a fossil bank, then different fossils will occur.Independent Variable: Depth of soil

Modifications 5 10 15 20 25# of Trials1 1 1 1 1

Dependent Variable: Amount and type of fossils.Constant: 1 bucketControl ?

Aloe vera and PlanariaAloe vera and Planaria

James read that Aloe vera promoted healing of burned tissue. He decided to investigate the effect of varying amounts of aloe vera and regeneration of planaria. He bisected the planaria to obtain 10 parts (5 heads and 5 tails) for each experimental group. He applied concentrations of 0%, 10%, 20%, and 30% Aloe vera to the groups. Fifteen ml of Aloe vera solutions were applied. All planaria were maintained in a growth chamber with identical food, temperature, and humidity. On day 15, James observed the regeneration of the planaria parts and categorized developed as full, partial, or none.

Experimental Design DiagramExperimental Design Diagram

Title: The effect of aloe vera on regeneration of planaria.

Hypothesis: If more aloe vera is used then there will be an increased amount of planaria regeneration.

Independent Variable: Percentage of Aloe VeraModifications10% 20% 30%# of Trials 10 10 10

Dependent Variable: amount of regenerationConstant: food, temperature, humidityControl : 0% aloe vera

Experimental Design Experimental Design and Scienceand Science

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