Lines of Best Fit Flashcards

All 6 cards in this deck

What is a line of best fit on a scatter graph?

A single straight line drawn through the middle of the points, following the trend, with roughly equal numbers of points on each side.

True or false? A line of best fit must pass through the origin.

False. It just has to follow the trend of the points — it should not be forced through the origin or through one particular point.

What are the steps to estimate a value from a scatter graph using a line of best fit?

e.g. estimate the Maths mark of a student with a Science mark of $34$ (Science on the $x$-axis)

1. Draw a suitable straight line of best fit.
2. Draw a line up from the known value on its axis to the line of best fit: up from $x = 34$.
3. Read across to the other axis: gives an estimated Maths mark of about $38$.

What is interpolation when using a line of best fit?

Estimating a value that lies inside the range of the plotted data, which makes the estimate reasonably reliable.

Why may an estimate found by extending a line of best fit beyond the plotted points be unreliable?

Because it is extrapolation — the value is outside the range of the data, so the trend may not continue.

What does the gradient of a line of best fit tell you in context?

e.g. ship width (m) against ship length (m), gradient $0.15$

The average change in the $y$-variable for each increase of $1$ in the $x$-variable: width increases by about $0.15$ m for each extra metre of length.