Name __________________ Block __________________ Experimental Design Controls, Variables & Graphs Definition of a Variable: Something that is changed. In scientific experiments there are two variables; one that you control and one that is the result. Definition of an Independent Variable: “The Cause” The one thing that is changed in an experiment. On a graph it is on the horizontal (x) axis. Definition of a Dependent Variable: “The Effect” The result of the experiment. The dependent variable is whet is being measure. The result ‘depends’ on what the experimenter changed. On a graph, it is on the vertical (y) axis. A Control: A control is what we are comparing our experiment to; our ‘normal’ or ‘original’ state. ------------------------------------------------------------------------Directions – In the following statements, identify the independent and dependent variables. 1. Experiment Question: Does the varying depths of the ocean have different temperatures? Experiment Set-up: The temperature of the ocean was measured at various depths. Independent variable: _________________ 2. Experiment Question: Does the amount of time you study make a positive difference on test scores? Experiment Set-up: Study times were changed for each of the next three exams. First exam: 30 min of studying per week Second exam: 60 min of studying per week Third exam: 90 min of studying per week Independent variable: _________________ 3. Dependent Variable: _________________ Experiment Question: Do lemon trees receiving the most water produce the largest lemons? Experiment Set-up: Plants of the same age and height were given varying amounts of water. Independent variable: _________________ 4. Dependent Variable: _________________ Dependent Variable: _________________ Experiment Question: Does keeping the lights on for different amounts of time each day effect the number of eggs a hen lays? Experiment Set-up: Different hens were put into different lighted environments. Independent variable: _________________ Dependent Variable: _________________ 5. Experiment Question: Does Gatorade effect the running times of milers? Experiment Set-up: Runners drank varying volumes of Gatorade and their mile times were recorded Independent variable: _________________ 6. Experiment Question: Does the temperature surrounding a corn crop effect how soon the corn sprouts? Experiment Set-up: Corn plants were placed in various heated green-houses and the sprout time was recorded. Independent variable: _________________ 7. Dependent Variable: _________________ Experiment Question: Does poor attendance of students in Biology class effect their grades in that class? Experiment Set-up: The teacher compared student attendance rates against student grades. Independent variable: _________________ 8. Dependent Variable: _________________ Dependent Variable: _________________ Experiment Question: Does the amount of Vitamin A that rats eat affect their weight? Experiment Set-up: 25 rats were weighed and then placed into five different groups of 5 rats each. All animals are fed identical diets except for the amount of vitamin A they receive. Each groups gets a different amount of vitamin A. After 3 weeks of diet, the rats are weighed again. Independent variable: _________________ Dependent Variable: _________________ There can be several controlled variables. If an experiment is to be useful, only one variable at a time can be manipulated intentionally. All other variables must be controlled throughout all parts of the experiment. If more than one variable is altered (changed), the results of an experiment cannot be interpreted with any validity. 9. An experiment was performed to determine how the amount of coffee grounds could affect he taste of coffee. The same kind of coffee, the same percolator (coffee machine), the same amount and type of water, the same perking time, and the same electrical sources were used. Independent variable: _________________ Controls/constants: 1. ____________________________________ 2. 3. ____________________________________ 10. Dependent Variable: _________________ ____________________________________ A student wanted to test how the mass of a paper airplane affected the distance it would fly. Paper clips were added before each test flight. As each paper clip was added, the plane was tested to determine how are it would fly. Independent variable: _________________ Dependent Variable: _________________ What are two controls that would need to be in place in this experiment to make the results valid: 1. _____________________________________________________________ 2. _____________________________________________________________ In all experiments, it is important that controls are kept constant and that only variable at a time be tested so that appropriate conclusions can be made. In the following ‘experiments’, please explain what is wrong with the conclusion/claim. ----------------------------------------------------------11. A scientist is testing a new vaccine for colon-cancer patients. He gives 1(one) cup of Drug A to patient #1. He gives 2(two) cups of Drug B to patient #2. Patient #2 is cured of cancer. The scientist concludes that Drug B can cure patients of colon-cancer. What is the claim? What evidence to make the claim? What is wrong with the REASONING that connects the evidence to the claim? ----------------------------------------------------------12. A marine biologist wants to see if a particular fish survives better in salt water or in fresh water. She takes a bucket of live fish and places them in a salt-water pond in Alaska. She also takes a bucket of fish and places them in a fresh water pond in San Diego. The fish in the Alaskan pond die. She concludes the fish do better in fresh water. What is the claim? What evidence to make the claim? What is wrong with the REASONING that connects the evidence to the claim? 13. 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 What should the claim/conclusion be? What is the Independent Variable (IV)? What is the Dependent Variable (DV)? How could this experiment be improved? ----------------------------------------------------------14. Mr. Krabs wants to make Bikini Bottoms a nicer place to live. He has created a new sauce that he thinks will reduce the production of body gas associated with eating crabby patties from the Krusty Krab. He recruits 100 customers with a history of gas problems. He has 50 of them (Group A) eat crabby patties with the new sauce. The other 50 (Group B) eat crabby patties with sauce that looks j ust like new sauce but is really just mixture of mayonnaise and food coloring. Both groups were told that they were getting the sauce that would reduce gas production. Two hours after eating the crabby patties, 30 customers in group A reported having fewer gas problems and 8 customers in group B reported having fewer gas problems. What is the Control Group? What is the Independent Variable (IV)? Identify the hypothesis/claim be. What is the Dependent Variable (DV)? Explain what factors in the experiment might be possible sources of experimental error? Why do you think 8 people reported feeling better? ----------------------------------------------------------What is a Blind Study (sometimes called a How could this experiment be changed to truly Double Blind Study)? explain why the 8 people that felt better? What does the x-axis represent? What does the y-axis represent? What are some observations that you can make based on the graph? What do you foresee happening in the next 10 years? Graph of the Week November___________, 2018 future? What inf graph? Graph of the Week Questions to ask when reading graphs: Directions: Analyze the graphs below and write a reflection/answer the questions below about what Is there an upward or downward youAnalyze thinkthethe graphs communicating to you. Tothe guide starttrend? with some __________________________ graphs below are and write a reflection on what you think graphsyou with your response, Are there any sudden spikes in the observations. are communicating to you. To guide you with your response, start with some graph? __________________________ observations. What is being compared in the graph? What prediction can I make for the is thetopics topic ofof each - WhatWhat are the thegraph? graphs? __________________________ future? does theare x-axis represent? What does(If thethere y-axis represent? - WhatWhat quantities being compared? are x- and y- axes, what do they represent?) What inferences can I make about the __________________________ are some observations that youyou can make based on the graph? - WhatWhat are some observations that can make based on the graphs? graph? do you foresee happening happening in the years? __________________________ - WhatWhat do you foresee in next the 10 next 10 years? 1 2 3 4 5 - Are there any upward or downward trends? Does this trend tell us anything? __________________________ _____________________________________________ __________________________ _____________________________________________ __________________________ _____________________________________________ _____________________________________________ __________________________ _____________________________________________ __________________________ _____________________________________________ _____________________________________________ __________________________ _____________________________________________ __________________________ _____________________________________________ _____________________________________________ __________________________ _____________________________________________ _____________________________________________ __________________________ _____________________________________________ ____________________________________________ _____________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ _______________________________________________________________ ____________________________________________ _______________________________________________________________ ____________________________________________ __________________________________________________________________________________________________ ____________________________________________ ____________________________________________ ____________________________________________ ____________________________________________ ____________________________________________ _______________________________________________________________________________
