levo

Geographical Skills

Correlation, lines of best fit and Spearman's rank

  • 3 things to know
  • Components 01, 02 and 03

Overview

Recall questions on positive and negative correlation, correlation and causation, lines of best fit, residuals and extrapolation, Spearman's rank correlation coefficient, its formula and tied ranks, worked calculations for an outwash plain and an alluvial fan, null hypotheses, significance at the 0.05 level and critical values, and why small samples are unreliable.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

What is correlation?

Process

How are tied values ranked when calculating Spearman's rank?

Key term

What is a residual on a scatter graph?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is correlation?

    Model answer

    Correlation is the extent to which two variables change together, described by its direction, positive or negative, and its strength, from strong to weak.

  2. 2

    Distinguish between positive and negative correlation, with a geographical example of each.

    Model answer

    In a positive correlation both variables rise together, such as wave height and fetch, whereas in a negative correlation one falls as the other rises, such as grain size and distance from the apex of an alluvial fan.

  3. 3

    Why does a correlation not prove that one variable causes a change in the other?

    Model answer

    Both variables may be driven by a third factor or the link may be coincidence, so a cause has to be established by geographical explanation rather than by the statistic alone.

  4. 4

    How should a line of best fit be drawn on a scatter graph?

    Model answer

    As a single straight line following the trend of the points, with roughly equal numbers of points on either side, ideally passing through the point plotted at the mean of both variables.

  5. 5

    What is a residual on a scatter graph?

    Model answer

    A residual is the vertical distance between an observed point and the line of best fit, and a large residual marks an anomaly that needs explaining.

  6. 6

    Why is it risky to extrapolate a line of best fit beyond the data?

    Model answer

    The relationship may change or break down outside the range that was measured, so a prediction made far beyond the observed values, such as future glacier retreat, can be badly wrong.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Coastal Landscapes
Glaciated Landscapes
Dryland Landscapes
Earth’s Life Support Systems

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Hotter magma is .
runnierthickerslower

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe lower quartile is the 2nd value, 11 cm.
BThe upper quartile is the 6th value, 16 cm.
CThe interquartile range is 16 − 11 = 5 cm.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

The sunspot cycle lasts about 11 years.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Geographical Skills, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Or £46 a year, about £3.83 a month. Cancel anytime.