Foundation and Higher · scatter graphs

Scatter graphs.
Correlation and
line of best fit.

and what you
cannot conclude

do two things move together —

Correlation

positive: both go up together

negative: one up, the other down

step 1 of 4

Plot and describe

1. Each cross is one student.

2. More revision, higher score.

✓ Positive correlation

step 2 of 4

1. One straight line, drawn with a ruler.

2. Through the middle, balanced each side.

✓ It does not have to go through (0, 0)

step 3 of 4

1. 6 hours: go up to the line, then across.

2. Read off the score: about 66.

✓ Draw the lines on: they earn the mark

step 4 of 4

1. An outlier does not fit the pattern.

2. Beyond the data it may not hold.

✓ Correlation does not prove cause

scatter graphs —

Correlation

positive, negative or none

Line of best fit

ruler, through the middle

Estimate

only inside the data

Describe it in context: “as revision
time goes up, scores go up”.

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