ACT Science Flashcards: Variables And Controls

What this deck covers

This deck focuses on Variables And Controls, giving you a quick way to review the definitions, rules, and examples that matter most for ACT Science.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: Define 'independent variable' in an experiment.

Answer: An independent variable is the variable that is changed or controlled in a scientific experiment. It's manipulated by researchers to observe its effect on other variables.

Flashcard 2: Identify the independent variable: Water temperature is changed; dissolved oxygen is measured.

Answer: Water temperature. This is the factor being deliberately manipulated.

Flashcard 3: What is the primary purpose of a double-blind experiment?

Answer: To prevent bias by ensuring neither participants nor researchers know who is receiving a treatment. It eliminates expectation effects that could bias results.

Flashcard 4: What is the effect of a confounding variable on experimental results?

Answer: It may distort the perceived effect of the independent variable on the dependent variable. It creates false correlations and misleading conclusions about causation.

Flashcard 5: In a drug trial, which group receives a placebo?

Answer: Control group. The placebo group serves as a control for comparison.

Flashcard 6: What term describes variables other than the independent variable that can affect results?

Answer: Confounding variables. These are unwanted variables that can distort experimental results.

Flashcard 7: Identify the independent variable: Measuring reaction time under different light conditions.

Answer: Light condition. This is what researchers deliberately vary between test conditions.

Flashcard 8: What is a positive control?

Answer: A control expected to produce a known effect to verify the setup works. Confirms the experimental system is functioning properly.

Flashcard 9: What is a controlled variable (constant) in an experiment?

Answer: A factor kept the same across all trials. Prevents other factors from influencing the results.

Flashcard 10: What is a positive control?

Answer: A control expected to produce a known effect to verify the setup works. Confirms the experimental system is functioning properly.

Flashcard 11: Identify the controlled variable: Comparing reaction rate at 20^ vs 30^ using same volume.

Answer: Solution volume. Volume must stay constant to isolate temperature's effect.

Flashcard 12: Identify the dependent variable: Measuring the effect of exercise intensity on pulse rate.

Answer: Pulse rate. This measures the cardiovascular response to activity.

Flashcard 13: What is a hypothesis in the context of variables?

Answer: A hypothesis is a proposed explanation for a phenomenon, predicting relationships between variables. It predicts how changing one variable affects another.

Flashcard 14: What is random assignment used for in experiments?

Answer: To reduce bias by distributing confounders across groups. Ensures groups are comparable by equalizing unknown factors.

Flashcard 15: In an experiment, why is it crucial to have a well-defined control group?

Answer: To ensure that the results can be attributed to the experimental treatments rather than other factors. A proper control isolates the treatment effect from other influences.

Flashcard 16: What is blinding in an experiment?

Answer: Keeping subjects and/or researchers unaware of group assignments. Prevents expectations from influencing behavior and results.

Flashcard 17: What is the operational definition of a variable?

Answer: A precise description of how it is measured or manipulated. Makes the variable concrete and measurable for scientific study.

Flashcard 18: What distinguishes a control group from an experimental group?

Answer: A control group is not exposed to the independent variable, unlike the experimental group. Control groups don't receive the experimental treatment.

Flashcard 19: In an experiment, what does a constant refer to?

Answer: A constant is a factor that does not change throughout the experiment. Constants ensure that only the independent variable affects the results.

Flashcard 20: Which axis usually displays the independent variable on a graph?

Answer: The $x$-axis. Convention places the manipulated variable on the horizontal axis.

Flashcard 21: What is blinding in an experiment?

Answer: Keeping subjects and/or researchers unaware of group assignments. Prevents expectations from influencing behavior and results.

Flashcard 22: Identify the controlled variable: Comparing reaction rate at 20^ vs 30^ using same volume.

Answer: Solution volume. Volume must stay constant to isolate temperature's effect.

Flashcard 23: Which axis usually displays the dependent variable on a graph?

Answer: The $y$-axis. Convention places the measured response on the vertical axis.

Flashcard 24: What is the role of randomization in controlling variables?

Answer: To reduce bias by evenly distributing confounding variables across groups. Random assignment prevents systematic differences between groups.

Flashcard 25: Identify one reason why controls are important in experiments.

Answer: They help ensure that the results are due to the independent variable. Controls eliminate alternative explanations for observed changes.

Flashcard 26: What does it mean to control a variable?

Answer: To control a variable means to keep it constant throughout the experiment. This prevents the variable from influencing results.

Flashcard 27: Identify the variable that must be held constant: Comparing battery brands by flashlight brightness.

Answer: Same flashlight and bulb. Different equipment could affect brightness measurements.

Flashcard 28: Find the dependent variable: A spring is loaded with different masses; extension is recorded.

Answer: Spring extension. Extension is the measured response to different masses.

Flashcard 29: What is the dependent variable in an experiment?

Answer: The measured outcome that responds to the independent variable. This is what changes in response to the independent variable manipulation.

Flashcard 30: What term describes variables other than the independent variable that can affect results?

Answer: Confounding variables. These are unwanted variables that can distort experimental results.

Flashcard 31: Identify the variable type: Reaction time in response to a stimulus.

Answer: Dependent variable. Reaction time is measured as a response to the stimulus treatment.

Flashcard 32: Which variable should be controlled: Testing light intensity on photosynthesis using identical plants?

Answer: Plant species (use the same species for all groups). Different species could respond differently to light intensity.

Flashcard 33: Identify the independent variable: Studying the effect of diet on energy levels.

Answer: Diet type. This is what researchers deliberately change between groups.

Flashcard 34: What is the experimental group in an experiment?

Answer: The group receiving the treatment or manipulated condition. This group experiences the variable being tested.

Flashcard 35: Which variable is manipulated by the experimenter?

Answer: Independent variable. This is the factor researchers intentionally change or vary.

Flashcard 36: What is the best reason to include multiple levels of the independent variable?

Answer: To detect trends and estimate the relationship across a range. Reveals patterns and allows interpolation between tested values.

Flashcard 37: State the role of a control group in an experiment.

Answer: A control group is used as a baseline to compare results with the experimental group. It shows what happens without experimental treatment.

Flashcard 38: Identify the dependent variable: Effect of sunlight on plant height.

Answer: Plant height. This is what gets measured as the outcome variable.

Flashcard 39: Which variable is measured in response to changes made by the experimenter?

Answer: Dependent variable. This variable shows the effect of experimental manipulation.

Flashcard 40: What type of variable is 'age of participants' in a study on exercise?

Answer: Independent variable. Age is a factor that researchers can select or manipulate in their study design.

Flashcard 41: What role do constants play in an experiment?

Answer: Constants ensure that the experiment tests only the effect of the independent variable on the dependent variable. They prevent unwanted variables from affecting outcomes.

Flashcard 42: What is an independent variable?

Answer: An independent variable is the variable that is changed or controlled in a scientific experiment. This is the factor deliberately manipulated by researchers.

Flashcard 43: What is the purpose of using a placebo in experiments?

Answer: To serve as a control treatment to compare against the effects of the drug being tested. Placebos control for psychological effects unrelated to the actual drug.

Flashcard 44: What is the main goal of a controlled experiment?

Answer: To test the effect of an independent variable on a dependent variable while controlling other variables. Controls ensure that observed effects are due to the independent variable alone.

Flashcard 45: What is a dependent variable?

Answer: A dependent variable is the variable being tested and measured in a scientific experiment. This responds to changes in the independent variable.

Flashcard 46: In an experiment, what does the dependent variable depend on?

Answer: The changes made to the independent variable. The dependent variable responds to manipulations of the independent variable.

Flashcard 47: In a study of the effect of temperature on solubility, identify the independent variable.

Answer: Temperature. Temperature is the factor being manipulated to test its effect.

Flashcard 48: Why is it important to control variables in an experiment?

Answer: To isolate the effect of the independent variable on the dependent variable. Control ensures observed changes are due to the intended treatment only.

Flashcard 49: Identify the independent variable: Testing sound levels on plant growth.

Answer: Sound level. This is what researchers deliberately manipulate between groups.

Flashcard 50: What is a confounding variable?

Answer: A factor that changes with the independent variable and affects the dependent variable. Makes it difficult to determine what actually caused the observed effect.

Flashcard 51: Which variable is expected to change when the independent variable is altered?

Answer: Dependent variable. The dependent variable responds to changes in the independent variable.

Flashcard 52: Why is it important to have a control group?

Answer: It helps to isolate the effect of the independent variable by providing a comparison baseline. It shows what happens without the experimental treatment.

Flashcard 53: What is a confounding variable?

Answer: A confounding variable is an outside influence that changes the effect of a dependent and independent variable. It creates false relationships between variables being studied.

Flashcard 54: Identify the dependent variable: Water temperature is changed; dissolved oxygen is measured.

Answer: Dissolved oxygen concentration. This is the response being measured.

Flashcard 55: Identify the dependent variable: Effect of sunlight on plant height.

Answer: Plant height. This is what gets measured as the outcome variable.

Flashcard 56: Identify the dependent variable: Analyzing the impact of diet on weight loss.

Answer: Weight loss. This measures the outcome researchers want to study.

Flashcard 57: What is the difference between random assignment and random sampling?

Answer: Assignment places subjects in groups; sampling selects subjects from a population. Assignment creates comparable groups; sampling represents populations.

Flashcard 58: In a drug trial, which group receives a placebo?

Answer: Control group. The placebo group serves as a control for comparison.

Flashcard 59: Identify the dependent variable: Analyzing the impact of sleep on memory retention.

Answer: Memory retention. This measures how well information is recalled.

Flashcard 60: Define a positive control.

Answer: A positive control is a group expected to produce a positive result, confirming that the experiment setup is capable of producing results. It proves the experimental system works as expected.

Flashcard 61: What is a confounding variable?

Answer: A confounding variable is an outside influence that changes the effect of a dependent and independent variable. It creates bias by affecting the relationship between variables being studied.

Flashcard 62: What distinguishes a control group from an experimental group?

Answer: A control group is not exposed to the independent variable, unlike the experimental group. Control groups don't receive the experimental treatment.

Flashcard 63: Which variable is measured in response to changes made by the experimenter?

Answer: Dependent variable. This variable shows the effect of experimental manipulation.

Flashcard 64: What is a negative control?

Answer: A control expected to show no effect to detect background changes. Helps identify unexpected changes not caused by the treatment.

Flashcard 65: What is the placebo effect?

Answer: A change caused by expectation rather than the treatment itself. Shows how beliefs alone can produce measurable effects.

Flashcard 66: Identify the independent variable: Plant growth with different fertilizers.

Answer: Type of fertilizer. This is what the experimenter deliberately changes between groups.

Flashcard 67: What is the most common reason correlation does not imply causation?

Answer: A confounding variable may cause both observed changes. A third factor may independently influence both variables.

Flashcard 68: What is the role of randomization in controlling variables?

Answer: To reduce bias by evenly distributing confounding variables across groups. Random assignment prevents systematic differences between groups.

Flashcard 69: Identify the independent variable: Measuring learning with different study techniques.

Answer: Study technique. This is what researchers deliberately vary between groups.

Flashcard 70: Identify the control variable: Testing plant growth in various soil types.

Answer: Plant species. Soil type varies, so plant species must remain constant.

Flashcard 71: What is the most common reason correlation does not imply causation?

Answer: A confounding variable may cause both observed changes. A third factor may independently influence both variables.

Flashcard 72: Identify the dependent variable: Different salt concentrations; time to boil is measured.

Answer: Time to boil. This is the response being measured.

Flashcard 73: Which axis should show time if you measure temperature as time passes?

Answer: The $x$-axis. Time is the manipulated variable affecting temperature.

Flashcard 74: Which variable is expected to change when the independent variable is altered?

Answer: Dependent variable. The dependent variable responds to changes in the independent variable.

Flashcard 75: Identify the type of variable: Speed of a car measured after applying different brakes.

Answer: Dependent variable. Speed is measured as a response to the brake type treatment.

Flashcard 76: What is the purpose of having a control group in an experiment?

Answer: To provide a standard for comparison against the experimental group. It establishes a baseline to determine if the treatment has an effect.

Flashcard 77: In an experiment, what does a constant refer to?

Answer: A constant is a factor that does not change throughout the experiment. Constants ensure that only the independent variable affects the results.

Flashcard 78: What is the placebo effect?

Answer: A change caused by expectation rather than the treatment itself. Shows how beliefs alone can produce measurable effects.

Flashcard 79: Define a controlled experiment.

Answer: A controlled experiment tests the effect of a single variable while keeping others constant. Only one variable changes while others remain constant.

Flashcard 80: Which type of variable is measured to assess the effect of the independent variable?

Answer: Dependent variable. This variable responds to changes in the independent variable.

Flashcard 81: Define a negative control.

Answer: A negative control is a group where no response is expected, ensuring that the experimental setup does not produce false positives. It confirms no response occurs without treatment.

Flashcard 82: In a study on sleep and alertness, what is an independent variable?

Answer: Amount of sleep. Sleep amount is manipulated to observe its effect on alertness.

Flashcard 83: Identify the independent variable: Plant growth with different fertilizers.

Answer: Type of fertilizer. This is what the experimenter deliberately changes between groups.

Flashcard 84: Identify the independent variable: A catalyst is present or absent; reaction time is measured.

Answer: Presence of the catalyst. Catalyst presence/absence is the manipulated condition.

Flashcard 85: What is a variable in a scientific experiment?

Answer: A variable is any factor, trait, or condition that can exist in differing amounts or types. It can be qualitative or quantitative and varies between subjects or conditions.

Flashcard 86: Identify the independent variable: Different salt concentrations; time to boil is measured.

Answer: Salt concentration. This is the variable being deliberately changed.

Flashcard 87: Identify the variable type: Amount of sunlight a plant receives in a growth study.

Answer: Independent variable. Sunlight is manipulated by the researcher to test its effect on growth.

Flashcard 88: Identify the dependent variable: Plants get $0$, $5$, or $10$ mL fertilizer; height is measured.

Answer: Plant height. This is what's measured to assess the fertilizer's effect.

Flashcard 89: What is a dependent variable?

Answer: A dependent variable is the variable being tested and measured in an experiment. It responds to changes in the independent variable.

Flashcard 90: What is a trial in an experiment?

Answer: One run or repetition of the procedure. Multiple trials help ensure results are reliable and repeatable.

Flashcard 91: What is the term for a variable that is not controlled and affects the outcome?

Answer: Confounding variable. Uncontrolled variables can create false conclusions about cause and effect.

Flashcard 92: In a study on sleep and alertness, what is an independent variable?

Answer: Amount of sleep. Sleep amount is manipulated to observe its effect on alertness.

Flashcard 93: Define a control variable.

Answer: A control variable is a factor that is kept constant to prevent its influence on the outcome. Maintaining constancy prevents it from affecting experimental results.

Flashcard 94: Identify the independent variable: A catalyst is present or absent; reaction time is measured.

Answer: Presence of the catalyst. Catalyst presence/absence is the manipulated condition.

Flashcard 95: What is an experimental group?

Answer: An experimental group is exposed to the independent variable to test its effect. This group receives the treatment being tested.

Flashcard 96: Identify the independent variable: Studying the effect of diet on energy levels.

Answer: Diet type. This is what researchers deliberately change between groups.

Flashcard 97: Identify the dependent variable: Analyzing the impact of sleep on memory retention.

Answer: Memory retention. This measures how well information is recalled.

Flashcard 98: Identify the confounder: Coffee intake and test scores correlate, but coffee drinkers sleep less.

Answer: Sleep amount. Sleep affects test performance independently of coffee intake.

Flashcard 99: Why is it important to control variables in an experiment?

Answer: To isolate the effect of the independent variable on the dependent variable. Control ensures observed changes are due to the intended treatment only.

Flashcard 100: Which type of variable is manipulated by the researcher?

Answer: Independent variable. Researchers deliberately change this variable to test its effects.