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Teaching video
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Grade 8 chapters and video availability01 · Read and understand
What you will learn
- Explain how to read a scatter plot without claiming causation.
- Solve the two practice problems and explain how the assumptions affect the answers.
Before you start
Coordinate plotting and positive slope.
Keep paper nearby. Read the question once for the context, then again to identify what is known and what you need to find.
Start with a question
A made-up data set pairs outdoor temperature with ice-cream sales: (15,20), (20,35), (25,50), (30,65). Describe the association and explain why it does not by itself prove a causal rule.
Why this math matters
A scatter plot can show direction, form, and unusual points, but an association alone does not identify a cause. Describe direction and shape before proposing an explanation, and distinguish observations from experimental evidence.
Set up the model
A useful answer starts with clear assumptions:
- Temperature and sales are paired for the same observation periods.
- These four fictional observations are observational, not a randomized experiment.
02 · Work through the example
Follow the reasoning, one step at a time.
Try to predict the next step before reading it. After each calculation, explain why the operation makes sense and how it helps answer the original question.
Work through it with Amar
See this example unfold.
The complete worked example, one idea at a time.
Read a scatter plot without claiming causation
PausedQuestion: Start with the question. Paused.
Question
Start with the question
A made-up data set pairs outdoor temperature with ice-cream sales: (15,20), (20,35), (25,50), (30,65). Describe the association and explain why it does not by itself prove a causal rule.
Before you calculate
Read what is known and what you need to find. Make a prediction before moving to the first calculation.
Starts paused. Play advances through the full text at a reading pace; pause whenever you need more time. Previous, Next, and the phase buttons let you set your own pace. Playback pauses when this walkthrough leaves the screen or you switch tabs.
Your device’s reduced-motion setting keeps each phase still. Manual controls remain available. The full written solution stays below.
Represent the quantities
As temperature rises by 5, sales rise by 15
The data show a positive linear pattern across the listed points.
Apply the relationship
observed rate = 15/5 = 3 sales per temperature unit
This summarizes the pattern in the sample, not a universal physical law.
Check and interpret
Positive association is observed; causation is not established
Season, foot traffic, promotions, or other factors could also vary with temperature.
The result
Positive association is observed; causation is not established
Season, foot traffic, promotions, or other factors could also vary with temperature.
Common mistakes to catch
- Correlation or a visible trend alone does not establish cause and effect.
- No linear pattern does not mean no possible relationship.
03 · Practice independently
Try it before revealing the answer.
Use paper or a calculator as needed. Write your units and reasoning, then open the hint or explanation to check your approach.
Practice 1
A scatter plot trends downward as x increases. What direction of association is shown?
Show a hint
Describe the typical movement in y.
Reveal answer and explanation
Negative association
Higher x values tend to occur with lower y values.
Practice 2
If a scatter plot has a curved U-shape, does a weak straight-line pattern imply no relationship?
Show a hint
Look for forms beyond a straight line.
Reveal answer and explanation
No
A strong nonlinear relationship can exist even when a straight-line summary is weak.
Take the idea with you
Describe direction and shape before proposing an explanation, and distinguish observations from experimental evidence.
04 · Reflect and continue
Can you explain it in your own words?
Before moving on, explain the main idea without looking at the worked example. Try both practice questions, check your reasoning, and name one mistake you now know how to avoid. Return to a step if you still need support.
Up next: Choose the denominator in a two-way table
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