"Experimental Design Practice"
Experimental Design How do you plan and conduct an experiment? Experiment It is the scientific way to prove whether your hypothesis is correct or not. It includes: materials and the procedure- that is what are you doing in the experiment, how it is set up, and what materials you are using. There are two set ups to every experiment: the experimental setup with the variable and controlled setup which is done under normal or ideal conditions. Variable It is one of the conditions that may effect the result of your experiment and it is what you change to determine if your hypothesis is correct or not. Independent/Manipulated Variable The variable that is changed on purpose or varies in an experiment. There should only be one variable for each experiment. Example: giving different amounts of water to same type of plant. Dependent/Respondent Variable –“RESULTS” The variable that changes in response to the independent variable. How it changes “depends” on the independent variable. It is the results that you measure or observe. Example: growing plants with different amounts of water(independent variable) you measure how they grew differently(dependent variable). Constants/Controlled Variables Factors that remain the same throughout the experiment. If factors like temperature, method of experimenting, etc. are allowed to vary they might affect the results in a confusing way. Repeated Trials & Sample Size The experiment is repeated at least a few times to collect as many measurements as is reasonable. Usually take an average of all the data points. Control Setup The experiment where the conditions are not changed but are kept ‘normal,’ ‘natural,’ or ‘ideal.’ It is the standard which the results from the experimental setup are compared with, to see if the changed variable make a difference. Experimental Design Practice Name Period: Date Identify: independent variable–double underline dependent variable ---circle constants-(controlled variables)—outline with a rectangle control experiment--highlight repeated trials/sample size--underline once #1. Ten radish seeds were planted in each of the five pots found around the house that each contained 2 kg of “Pete’s Potting Soil” and were grown in a greenhouse where the temperature and humidity and amount of light was kept the same. The pots were given the following amounts of distilled water each day for 40 days: Pot 1, 50 ml; Pot 2, 100 ml, Pot 3, 150 ml, Pot 4, 200 ml; Pot 5, 250 ml. Because Pot 3 received the recommended amount of water, it was used as a control part of the experiment. This experiment was repeated five times. The height of each plant was measured at the end of the experiment and represented in a growth chart and line graph. #2. Gloria wanted to find out if the color of food would affect whether kindergarten children would select it for lunch. She put food coloring into 4 identical bowls of mashed potatoes. The colors were red, green, yellow and blue. She also served a sample of potatoes that were of normal color. Each sample was served fresh and warm with a square of butter. Each child was asked to choose a scoop of potatoes from any of the colors offered. Gloria did this experiment using 100 students of the same age. She recorded the number of students that chose each color and made a bar graph.