Question 1
A student wants to investigate whether the number of hours of sleep affects reaction time. Which of the following correctly identifies the independent and dependent variables?No clue? Show me the answer
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Method #1Direct ApproachStep 1: Recall the definitions
The independent variable is the one that is chosen or controlled — it is the cause. The dependent variable responds to the independent variable — it is the effect.
Step 2: Determine which variable is controlled
In this investigation, the researcher would choose how many hours of sleep the subjects get. This makes hours of sleep the independent variable.
Step 3: Determine which variable responds
The reaction time is what gets measured — it responds to changes in sleep hours. This makes reaction time the dependent variable.
Step 4: Choose the correct answer
The correct answer is: Independent: hours of sleep; Dependent: reaction time. On a graph, hours of sleep would go on the x-axis and reaction time on the y-axis.
Method #2Process of EliminationStep 1: Identify what is being asked
We need to correctly identify which variable is independent (controlled/cause) and which is dependent (responds/effect).
Step 2: Eliminate: reaction time as independent
The option "Independent: reaction time; Dependent: hours of sleep" is wrong. You don't control your reaction time — you measure it. Sleep hours are what you would control.
Step 3: Eliminate: both are independent
"Both are independent variables" is incorrect. In any controlled investigation, one variable is chosen and the other responds. You cannot control both simultaneously.
Step 4: Eliminate: both are dependent
"Both are dependent variables" makes no sense — something must be causing the change. You cannot have a response without a cause.
Step 5: Select the correct answer
The remaining option, "Independent: hours of sleep; Dependent: reaction time", is correct. Sleep is controlled; reaction time responds.
Question 2
Which of the following research questions involves bi-variate data?No clue? Show me the answer
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Method #1Direct ApproachStep 1: Recall what bi-variate data means
Bi-variate data involves two variables and explores the relationship between them. A key clue is the phrase "relationship between" two things.
Step 2: Check each option for two variables
The question about fertiliser and sunflower height contains two variables: amount of fertiliser AND height of sunflowers. It also explicitly asks about a relationship between them.
Step 3: Confirm the other options are uni-variate
"Most popular sport" — one variable (sport choice). "Goals per player" — one variable (goals). "Average temperature" — one variable (temperature). All three are uni-variate.
Step 4: Choose the correct answer
The answer is "Is there a relationship between the amount of fertiliser used and the height of sunflowers?" — it has two variables and asks about their relationship.
Method #2Process of EliminationStep 1: What are we looking for?
We need a question that involves two variables. Uni-variate questions only measure or count one thing.
Step 2: Eliminate: most popular sport
"Most popular sport among Year 8 students" only collects data about one thing: which sport students prefer. This is uni-variate — eliminate it.
Step 3: Eliminate: goals per player
"How many goals did each player score" records one measurement (goals) for each player. This is uni-variate — eliminate it.
Step 4: Eliminate: average daily temperature
"Average daily temperature in July" is one variable (temperature) measured over time. This is uni-variate — eliminate it.
Step 5: Select the correct answer
The remaining option — fertiliser and sunflower height — involves two variables and a relationship between them. This is bi-variate data.
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