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101-B: Identify Variables 1

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101-B: Identify Variables 1

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Any number or quality that you can measure and can change. (Variables can be either qualitative or quantitative.)

A variable that is systematically changed .

A variable that is measured each time the independent variable is changed.

A variable that is intentionally kept the same.

Measurability:

Remember that the variable must be something measurable and what you are exactly measuring. It cannot be an abstract concept you want to measure. For example, suppose you are trying to measure happiness. "Happiness" is not a concept with a precise definition that can be measured and quantified. What you can do is give people a paper that asks "How happy are you right now on a scale from 1 - 10?" In this case, your variable is not "happiness" itself, but people's answer to the question "How happy are you right now on a scale from 1 - 10?"

(This is a much bigger problem issue in psychology and medicine than in physics. In physics, we typically deal with quantities that can be precisely measured. However, it still bears mentioning.)

Questions

  1. Your Question: You have a device that fires marbles from a cannon, and you want to know which cannon angle causes a marble to fly the farthest distance before hitting the ground.
    Your Procedure: You begin the cannon at 5 degrees, fire it, and then determine how far the marble flies before hitting the ground. You add 5 degrees and repeat, and continue adding five degrees each time you fire the cannon. Throughout this procedure, the marble cannon is kept on its lowest strength setting.
    1. What is the independent variable?
    2. What is the dependent variable?
    3. Identify one controlled variable.
  2. Your Question: Which make and model of car has the best gas mileage on the highway?
    Your Procedure: I drive a different make and model of car from Fall River to Boston on the exact same route each night. I drive in the middle o f the night, when there is very little traffic, and I use cruise control to make sure that I stay at a speed of 60 mph. After each trip, I chart precisely how much gas my car used.
    1. What is the independent variable?
    2. What is the dependent variable?
    3. Identify one controlled variable.
  3. Your Question: What is the fastest way to drive from home to work?
    Your Procedure: Every day, I leave my apartment at precisely 6:30 am, when traffic is light. I take a different route to work each day, and each day I make note of the time that I arrive at work.
    1. What is the independent variable?
    2. What is the dependent variable?
    3. Identify one controlled variable.
  4. Your Question: How long do you grill a steak to get the best taste?
    Your Procedure: Every night, I buy 30 T-Bone steaks. I grill the steaks for a different time interval every night, beginning with 8 minutes and adding one minute each night. I give the steaks free to people in Government Center in Boston. Each person fills out a survey on how the steak tastes.
    1. What is the independent variable?
    2. What is the dependent variable?
    3. Identify one controlled variable.
  5. Your Question: Does homework help students learn more?
    Your Procedure: I give each class different amount of homework. One class receives no homework. Another class receives about 5 physics problems, and another class receives about 50 physics problems. All students receive exactly the same After two weeks, I give all classes a physic test, and I calculate the mean score of each class.
    1. What is the independent variable?
    2. What is the dependent variable?
    3. Identify one controlled variable.
    4. Identify a variable I was not able to control.
  6. Your Question: I am an advertising designer, and I want to know: what type of TV advertisement sells the most hamburgers. (Those with giant photos of hamburgers? Those with people enjoying hamburgers with their friends? Ads about how cheap hamburgers are? Humorous ads?)
    Your Procedure: I create several different hamburger ads. I bring randomly selected volunteers into a room and show each volunteer one of the ads. I only select volunteers between ages 16 and 36. Three months later, I track each volunteer down and give them a survey on how many hamburgers they purchased in the past three months.
    1. What is the independent variable?
    2. What is the dependent variable?
    3. Identify one controlled variable.

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