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Flip to reveal answersWhat are the steps to perform linear regression on a TI-84 GDC?
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All 16 Flashcards — GDC regression and parameters
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Question
What are the steps to perform linear regression on a TI-84 GDC?
Answer
1. Enter x data in L1, y data in L2. 2. Stat → Calc → LinReg(ax+b). 3. Note a and b from output. 4. Write the equation y = ax + b.
Question
What does the GDC regression output show you?
Answer
The best-fit equation parameters (a, b, etc.) and the correlation coefficient r (or R² for non-linear).
Question
IB asks "use the GDC to find the regression equation." What must you write?
Answer
The full equation with all parameters to 3 s.f. E.g. y = 2.35x + 4.18. Include what regression type you used if asked.
Question
After running regression, IB says "use your equation to predict y when x = 10." What do you do?
Answer
Substitute x = 10 into the regression equation and calculate. Show the substitution clearly.
Question
Data curves upward steeply. Which regression types should you try?
Answer
Exponential (ExpReg) and power (PwrReg). Run both and compare R² values.
Question
Data oscillates regularly. Which regression is appropriate?
Answer
Sinusoidal regression (SinReg on TI-84).
Question
You run LinReg (R² = 0.61) and ExpReg (R² = 0.95). What should you do?
Answer
Use the exponential model — much higher R² means far better fit.
Question
IB gives a data table showing a constant ratio between successive y-values. Which regression?
Answer
Exponential regression (ExpReg). Constant ratio is the hallmark of exponential growth/decay.
Question
GDC ExpReg output: a = 2.3456, b = 0.8123 (for y = a · bˣ). How do you write the answer?
Answer
y = 2.35 · 0.812ˣ (all values to 3 s.f.).
Question
IB asks "Write down the values of a and b." Do you need to show GDC working?
Answer
No — just state the values clearly. "From GDC: a = 2.35, b = 0.812." No algebraic working is needed.
Question
GDC gives LinReg: y = 3.7x − 12.4. Find the predicted y when x = 5.
Answer
y = 3.7(5) − 12.4 = 18.5 − 12.4 = 6.1.
Question
Why must regression coefficients be rounded to 3 s.f. in IB answers?
Answer
IB expects 3 significant figures unless specified. Using fewer can cause errors in later parts; IB may not award accuracy marks if rounding is too severe.
Question
What does r = 0.99 tell you about a linear regression?
Answer
Very strong positive linear correlation. The model fits the data extremely well.
Question
What is the difference between r and R²?
Answer
r: Pearson correlation coefficient, ranges from −1 to 1, linear regression only. R²: coefficient of determination, ranges 0 to 1, applies to all regression types. R² = r² for linear.
Question
IB asks "Comment on the reliability of the model." R² = 0.72. What do you write?
Answer
The model has a moderate fit (R² = 0.72 — 72% of variation is explained). Predictions may not be highly reliable.
Question
R² = 1 for a regression. What does this mean?
Answer
Perfect fit — every data point lies exactly on the regression curve. All predicted values match observed values exactly.
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