By Janice VanCleave — John Wiley & Sons, Inc.

Updated on Feb 15, 2011

### Engineering

- What effect does the shape of an object have on its strength?
**Independent variable:**Shape of object**Dependent variable:**Strength - Which brand of antacid tablet is the best at neutralizing stomach acid?
**Independent variable:**Brand of antacid tablet**Dependent variable:**Degree of neutralization - Which brand of hair spray holds hair in place the longest time?
**Independent variable:**Brand of hair spray**Dependent variable:**Holding time - Which brand of toilet paper decomposes the fastest in water?
**Independent variable:**Brand of toilet paper**Dependent variable:**Rate of decomposition - Which brand of detergent has the most effect on stain removal from clothes?
**Independent variable:**Brand of detergent**Dependent variable:**Degree of stain removal - Which type of cloth is the most resistant to food stain?
**Independent variable:**Type of cloth**Dependent variable:**Degree of resistance to food stain - Which brand of shampoo produces the most lather?
**Independent variable:**Brand of shampoo**Dependent variable:**Amount of lather - What effect does borax concentration have on softening water?
**Independent variable:**Borax concentration**Dependent variable:**Degree of water softness - Which brand of washable colored markers does water most effectively remove from skin?
**Independent variable:**Brand of washable colored markers**Dependent variable:**Degree of water solubility

### Mathematics

- How does age affect the mean height of a group?
**Independent variable:**Age**Dependent variable:**Height - How does gender affect the mean height of a group?
**Independent variable:**Gender**Dependent variable:**Height - How does the height of a rain gauge affect the distance between scale measurements?
**Independent variable:**Height of rain gauge**Dependent variable:**Distance between scale measurements - How does the diameter of a rain gauge affect the distance between scale measurements?
**Independent variable:**Diameter of rain gauge**Dependent variable:**Distance between scale measurements

### Physics

- How does the length of the string of a stringed instrument affect pitch?
**Independent variable:**String length**Dependent variable:**Pitch - How does the thickness of the string of a stringed instrument affect pitch?
**Independent variable:**String thickness**Dependent variable:**Pitch - How does the volume of water in a glass bottle affect the pitch of the sound produced when the bottle is struck?
**Independent variable:**Volume of water**Dependent variable:**Pitch - How does the volume of water in a glass bottle affect the pitch of the sound produced when air is blown across the mouth of the bottle?
**Independent variable:**Volume of water**Dependent variable:**Pitch - How do the number of coils in a solenoid affect the strength of an electromagnet?
**Independent variable:**Number of coils in a solenoid**Dependent variable:**Magnetic strength - What effect does the intermittent use of a dry-cell battery have on its life?
**Independent variable:**Time intervals of use of a dry-cell battery**Dependent variable:**Length of life of a dry-cell battery - What effect does the type of material charged have on the time it holds a static charge?
**Independent variable:**Type of material**Dependent variable:**Time of holding a static charge - What effect does humidity have on the strength of a static charge?
**Independent variable:**Humidity**Dependent variable:**Strength of a static charge - What effect does temperature have on the strength of a static charge?
**Independent variable:**Temperature**Dependent variable:**Strength of a static charge - Which brand of battery lasts the longest?
**Independent variable:**Brand of battery**Dependent variable:**Time to discharge the battery - What effect does the wattage of a lightbulb have on the amount of light it emits?
**Independent variable:**Wattage of lightbulb**Dependent variable:**Amount of light - What effect does the number of strokes of a magnet on a nail have on the degree the nail is magnetized?
**Independent variable:**Strokes of a magnet on a nail**Dependent variable:**Degree of magnetism - How does the position of the fulcrum in a first-class lever affect the weight it can lift?
**Independent variable:**Fulcrum position**Dependent variable:**Weight lifted - How does the position of the fulcrum in a first-class lever affect the force needed to lift an object?
**Independent variable:**Fulcrum position**Dependent variable:**Force applied - What effect does temperature have on the elasticity of a rubber ball?
**Independent variable:**Temperature**Dependent variable:**Elasticity of a rubber ball (measured by the height the dropped ball bounces) - What effect does the amount of a lubricant have on friction between a marble rolling down a wooden incline?
**Independent variable:**Amount of lubricant**Dependent variable:**Amount of friction - What effect does the temperature of a lubricant have on friction between a marble rolling down an incline?
**Independent variable:**Temperature of lubricant**Dependent variable:**Amount of friction - What effect does the diameter of a string have on its strength?
**Independent variable:**String diameter**Dependent variable:**Strength (measured by supporting weight) - What effect does the number of fibers in a string have on its strength?
**Independent variable:**Number of fibers**Dependent variable:**Strength (measured by supporting weight) - What effect does the thickness of plastic have on the weight it will hold?
**Independent variable:**Thickness of plastic**Dependent variable:**Weight supported - How does wing shape affect flight distance of a glider?
**Independent variable:**Wing shape**Dependent variable:**Flight distance - What effect does the viscosity of a fluid material have on the buoyancy of an object in it?
**Independent variable:**Fluid viscosity**Dependent variable:**Object buoyancy - What effect does the density of an object have on its buoyancy in water?
**Independent variable:**Object density**Dependent variable:**Object buoyancy in water - In what type of light is fluorescent ink most effective?
**Independent variable:**Type of light**Dependent variable:**Effectiveness of fluorescent ink (measured by brightness) - What effect does the size of a prism have on the spectrum produced?
**Independent variable:**Prism size**Dependent variable:**Spectrum - What effect does the type of metal have on conducting heat?
**Independent variable:**Type of metal**Dependent variable:**Rate of heat conduction - What effect does paint color have on its colorfastness when exposed to solar energy?
**Independent variable:**Paint color**Dependent variable:**Degree of fading in sunlight - What effect does the mass of an object have on momentum?
**Independent variable:**Mass of object**Dependent variable:**Momentum

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