Mrs. Hankins' Classroom - Home



Tiffany was investing how fast it took Hayden to react to different sounds. Identify the dependent variable. (1 point)

|M|how much time it took Hayden to react |

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|M|playing the trumpet over and over |

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|M|different sounds |

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|M|Hayden |

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|M|how fast Hayden reacted |

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Nick wanted to see how high an ice cube would float in different temperatures of water. Identify the dependent variable. (1 point)

|M|height of ice cube |

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|M|size of ice cube |

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|M|temperature of water |

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|M|temperature the ice cube was at its' highest height |

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|M|amount of water |

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4. Justin usually blows his nose using Kleenex tissues. His snot keeps leaking through the tissue. He decided he is going to create an experiment to find out if there is something better. What is his independent variable? (1 point)

|M|mass of the snots the tissue can hold |

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|M|Justin |

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|M|type of tissue |

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|M|amount of tissue |

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|M|Kleenex |

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What is one control variable?

What is the control group?

Mario studied how far room temperature water would spurt out of a platic milk carton when 3mm holes were punched at different heights from the bottom of the container. Identify the independent variable. (1 point)

|M|3 mm holes |

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|M|distance water traveled out of carton |

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|M|different heights of holes in container |

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|M|ice water from Iceland |

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9. Mr. McNiece wanted to see how different types of music affected students' pulse rates. She played different types of music: heavy metal, rap, R&B, alternative, pop, country, and classical music. What constant should be considered when doing this experiment? (1 point)

|M|use all dead people |

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|M|types of music |

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|M|using a different student for each music type |

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|M|amount of time the music was played |

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Identify the independent variable and dependent variable(s) in the following experiments.

 

1. A researcher was interested in the effects of reward on intrinsic motivation. Some children were told that they would be given a special award for drawing with magic markers (an activity they already enjoyed). Other children were simply asked to draw with the magic markers. One week later, the children were unobtrusively observed for how much time they spent drawing with the markers. The children who expected and received a reward for drawing with the markers were less likely to draw with them later.

 

Independent Variable: Expected award or not

 

Dependent Variable: Time spent drawing with markers

 

2. In an investigation of the fundamental attribution error, subjects were given a speech to read that either favored or opposed Fidel Castro, the communist leader of Cuba. Subjects were told that the speech was written by a student who had been assigned to the position taken in the paper (that is, the student writing the speech had no choice on which position to take). Nevertheless, subjects believed that the student who wrote the pro-Castro speech had positive attitudes toward Castro, while subjects who read the anti-Castro paper believed the writer had negative attitudes toward Castro.

 

Independent Variable: Heard speech favoring or opposing Castro

 

Dependent Variable: Rating of speech writer’s attitude

 

3. Within a classroom setting, subjects were asked to listen to a guest instructor. All subjects were given a description of the instructor. Some subjects read a description containing the phrase “People who know him consider him to be a rather cold person...”, while other people read a description where the word “warm” was substituted for the word cold (otherwise, the descriptions were identical). After the lecture, subjects were asked to rate the instructor. Subjects who were told the instructor was warm gave him more favorable ratings compared to subjects who were told that the instructor was cold.

 

Independent Variable: Description of instructor as warm or cold

 

Dependent Variable: Ratings of instructor

 

 

4. Subjects watched a videotape of a woman taking an SAT-like test. In all cases, she correctly answered 15 out of 30 questions. But subjects who observed a pattern of initial success followed by failure perceived the woman as more intelligent than did those who observed the opposite pattern of failure followed by success.

 

Independent Variable: Pattern of success and failure

 

Dependent Variable: Intelligence rating

 

5. Subjects read about a woman who used a particular title, and then rated her on a number of traits. When the woman used the title Ms. rather than Miss or Mrs., she was assumed to be more assertive, achievement oriented, and dynamic, but also cold, unpopular, and unlikely to have a happy marriage.

 

Independent Variable: Type of title used

 

Dependent Variable: Rating of woman

 

6. People were randomly approached on the street by a stranger and were asked to use his camera to take a picture of him for a school project. For half of the subjects, the camera didn’t work--the stranger looked concerned, said that the camera was rather delicate, asked the subject if he touched any of the dials, and announced that it would have to be fixed. For the other half of the subjects, the camera worked fine. Further down the street, a woman dropped a file folder of papers. Forty percent of the subjects who had no broken-camera experience helped the woman pick up her papers, while 80% of the subjects who were led to believe that they broke the woman’s camera helped.

 

Independent Variable: Whether subjects believed they broke a camera or not

 

Dependent Variable: Helping pick up papers

Practice!

Identifying the independent variable, dependent variable, experimental and control conditions in an experiment.

Some tips!

➢ Start by identifying the dependent variable. What is actually being measured in the experiment? In the statement “a researcher is measuring the effect of chocolate on happiness”, the dependent variable is happiness, happiness is affected by chocolate, or happiness depends on chocolate.

➢ Identify the independent variable. If a researcher is measuring the effect of chocolate on happiness, the independent variable is chocolate. This is the variable that the experimenter will manipulate to see how it affects the dependent variable (in this case happiness).

➢ What is the experimental condition (experimental group)? What is the control condition (control group)? The control condition will be the one that is “business as usual.” If we are measuring the effect of chocolate (independent variable) on happiness (dependent variable), then the control group would get no chocolate. We say that the control group is not being exposed to the "treatment." In this case the treatment is chocolate, so the poor people in the control group are left chocolate-less. In order to find the experimental group, look at the group (or groups) that actually receives treatment, in this case, some specified amount of chocolate (some people have all the luck...).

For the following examples, identify

1) The dependent variable

2) The independent variable

3) The experimental condition(s)/experimental group(s)

4) The control condition/control group

Example 2

A researcher is curious to find out what effect classical music has on people’s level of relaxation (as measured by heart rate). He lets one group listen to classical music for one hour. He lets another group sit in a quiet room for one hour with no music. After one hour, he checks the heart rate of each person to measure their level of relaxation.

Example 3

A researcher conducts an experiment to assess the effects of alcohol on people's sense of balance. He divides his subjects into three groups: in one group the participants drink one ounce of alcohol, in another they drink two ounces of alcohol and in a third group the participants drink soda. He then watches as each participant tries to walk on a straight line from one corner of the room to the next and notes how many times they stumble outside the line.

ANSWERS!

Example 1

Aggression (or aggressive behavior) is the dependent variable. The researcher is studying the effect of sleep on aggression. In other words, the level of aggression depends on the amount of sleep. That is why it is called the dependent variable. It also says that the experimenter is monitoring (i.e., measuring) aggressive behavior. The dependent variable is always what is being measured. So aggressive behavior (or aggression) must be the dependent variable. The independent variable is the amount of sleep. Remember that the independent variable is the one that the researcher manipulates, which she clearly does in this case, letting some people sleep only 3 hours, and others only 6 hours.

Remember that the control group is not exposed to the treatment. In this particular case, we know that some people got to sleep as much as they want. This must then be the control group. You can think of the control group as “business as usual.” They are exposed to "normal conditions." The experimental groups in this case will be the group that sleeps 3 hours per night and the group that sleeps 6 hours per night. (Some experiments use only one experimental group, others use two or more. It all depends on what the experimenter wants to test).

Example 2

The dependent variable is the level of relaxation. How do we know? Well, the experimenter is looking at the effect of classical music on the level of relaxation. The state of relaxation depends on classical music. Again, look at what is being measured: the researcher is measuring the level of relaxation, as measured by heart rate. You would also be correct to say that the dependent variable is the heart rate, since this is the operational definition of the level of relaxation; this is how it is being measured. The independent variable is the classical music. The experimental condition is where they get to listen to classical music (they are exposed to the treatment - the classical music). The control condition, well, it is business as usual, they are just sitting in their quiet room.

Example 3

Dependent variable: sense of balance (as measured by number of "stumbles")

Independent variable: alcohol

Experimental condition: 2 experimental groups: drinking one and two ounces of alcohol

Control condition: drinking soda (business as usual, no active manipulation of the independent variable, i.e., no alcohol).

Practice- Independent and Dependent Variables

Remember: Time is frequently used as the independent variable. The dependent variable will change over time (this “change” is what the researcher measures/records).

Sample Problem: A scientist want to study the diversity of soil bacteria found during different

months of the year.

a. What is her Independent variable? _______________________________________

b. What will be her Dependent variable? ____________________________________

Questions. Identify the dependent and independent variables in the following examples.

1. Height of bean plants is recorded daily for 2 weeks.

a. Independent variable: ________________________________________________

b. Dependent variable: _________________________________________________

2. Guinea pigs are kept at different temperatures for 6 weeks. Weight gain is recorded.

a. Independent variable: ________________________________________________

b. Dependent variable: _________________________________________________

3. The diversity of algal species is calculated for a coastal area before and after an oil spill.

a. Independent variable: ________________________________________________

b. Dependent variable: _________________________________________________

4. Light absorption by a pigment is measured for red, blue, green, and yellow light.

a. Independent variable: ________________________________________________

b. Dependent variable: _________________________________________________

5. Batches of seeds are soaked in salt solutions for different concentrations and germination is counted for each batch.

a. Independent variable: ________________________________________________

b. Dependent variable: _________________________________________________

6. An investigator hypothesizes that the adult weight of a dog is higher when it has fewer littermates.

a. Independent variable: ________________________________________________

b. Dependent variable: _________________________________________________

Independent and Dependent Variables Practice

The independent variable is the one being tested. It’s the one thing you make different between tests.

The dependent variable is the result. It is what you measure at the end of the experiment.

1. The higher the temperature of water, the faster an egg will cook.

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2. An investigation was done to see if keeping the lights on for different amounts of time each day affected the number of eggs chickens lay.

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3. The time it takes to run a kilometer depends on the amount of exercise a person gets.

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4. Grass will grow taller if it is watered and fertilized a great deal.

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5. An investigation was performed to see if corn seeds would sprout at different times depending on the temperature of the air in which they were placed.

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6. The amount of algae growth in lakes seems to be directly related to the number of sacks of phosphate fertilizer sold by the local merchants.

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7. Lemon trees receiving the most water produce the largest lemons.

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8. The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead.

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9. Students in a science class carried out an investigation in which a flashlight was pointed at a screen. They wanted to find out if the distance from the light to the screen had any affect on the size of the illuminated area.

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10. The score on the final test depended on the number of study questions the student completed.

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11. A study was done with white rats to see if the number of offspring born with birth defects was related to the number of minutes of exposure to x-rays by the mother rats.

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12. Five groups of rats are fed identical diets except for the amount of vitamin A that they receive. Each group gets a different amount. After three weeks on the diet, the rats are weighed to see if the amount of vitamin A received has affected their weight.

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13. The state agriculture department has been counting the number of foxes in Brown county. Will the number of foxes have any affect on the rabbit population?

IV DV

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