# 1.2.e: Experimental Design

## Writing ExD’s

Directions

1. Pick one of the scenarios below.
2. Draw a picture that represents the experimental set-up. You can use numbers, letters, and simple drawings but be sure the full set up of the experiment is clear in your illustration. Remember to label the picture to include the different experimental groups
3. Use this information to write the Experimental Design for each experiment and Identify

a) Write a title for your experiment

b) Your hypothesis (If ____________, then ___________________)

c) The Independent Variable (IV): The independent variables represent inputs or causes. An independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable.

d) The Dependent Variable (DV) (The dependent variables represent the output or outcome whose variation is being studied. A dependent variable is the variable being tested and measured in a scientific experiment)

e) The constant variables: A constant variable is one that the researcher holds constant (controls) during an experiment.

4. Which of the experiment groups is use as a control (The groups whose conditions are in the most natural, unaffected state)

See example of submission: Design-Detective-Example.pdf

Actions

Scenarios

Scenario #1

While a construction crew was digging a pool in a backyard, Susan observed that different kinds and amounts of fossils were present in the area behind her house. She wondered if changes in fossil content occurred in some pattern as one dug from the surface to deeper areas. Susan marked the bank of the cliff at the end of their property at five positions. Starting at the surface, she marked every 5 meters: 0 (at the surface), 5, 10, 15, 20, and 25m from the surface. She removed 5 buckets of soil from each of the positions and determined the kind and number of fossils in each sample.

Scenario #2

Ten pea plant seeds were planted in each of 5 pots that contained 500g of “Peat’s Potting Soil.” The pots were given the following amounts of distilled water each day: Pot 1, 50ml; Pot 2, 100ml; Pot 3, 150ml; Pot 4, 200ml; Pot 5, 250ml. According to the pea seed package, the recommended of water for the pea plants was 150ml of water daily. After 40 days, the height of each plant was measured in centimeters.

Scenario #3

After studying about recycling, members of Mary’s biology class investigated the effect of various recycled products on plant growth. Mary’s lab group compared the effect of different aged grass compost on bean plants. Because decomposition is necessary for the release of nutrients, the group hypothesized that older grass would produce taller bean plants. Four flats of bean plants were planted with 15 plants in each flat. The plants were fertilized as follows: (a) Flat A: 150g of three month old compost, (b) Flat B: 150g of six month old compost, (c) Flat C: 150g of on month old compost. (d) Flat D: 0g of compost. The compost was made of the same materials and the plants received the same amount of sunlight and water each day. The plants grew for 20 days. After 20 days, the group recorded the height of each plant in centimeters.

Scenario #4

Sandy wanted to find out if the color of food would affect whether or not kindergarten children would select it for lunch. She put food coloring into 4 identical bowls of mashed potatoes. The colors were red, green, yellow, blue. One bowl of mashed potatoes was left as the regular white color. Each child was given the choice to choose the bowl of mashed potatoes of the color of their choice. Each day she recorded the choice of 100 different students. She did this for five days.