Edexcel A-Level Geography 9GE0
Tectonic Processes and Hazards
Glaciated Landscapes and ChangeLandscape
Coastal Landscapes and ChangeLandscape
Globalisation
Regenerating PlacesPlaces
Diverse PlacesPlaces
The Water Cycle and Water Insecurity
The Carbon Cycle and Energy Security
Superpowers
Health, Human Rights and InterventionConnections
Migration, Identity and SovereigntyConnections
Globalisation
Geographical skills: statistics, data and research ethics
- 3 things to know
- Papers 2 and 3
Overview
The skills examined across every topic: null hypotheses and significance, t-tests and a worked chi-squared test, Lorenz curves and the Gini coefficient, logarithmic scales, kite and dispersion diagrams, coding, research ethics and big data.
What you need to know
Answer each one before you reveal it.
Two samples of 10 have means 12.0 and 9.5 with standard deviations 2.0 and 2.5. Is the difference significant at p = 0.05 (critical value 2.10, 18 degrees of freedom)?
How are expected frequencies calculated for a chi-squared contingency table?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a null hypothesis, and what significance level is usually used?
Model answer
A statement that there is no relationship or difference between the variables; geographers usually reject it if the probability that the result arose by chance is below 5% (p = 0.05).
- 2
When is a t-test used, and what does it test?
Model answer
To test whether the means of two samples of interval data, which are roughly normally distributed, are significantly different, by dividing the difference between the means by their combined standard error.
- 3
When is a chi-squared test used, and how is it calculated?
Model answer
To test whether observed frequencies in categories differ significantly from expected frequencies: χ² = Σ(O − E)²/E, with expected frequencies usually the total divided equally among the categories.
- 4
Sixty pebbles are classified into three shape categories, with 30, 18 and 12 observed. Test whether they differ from an even distribution (critical value 5.99 at p = 0.05, 2 degrees of freedom).
Model answer
Expected frequencies are 20 each. χ² = 100/20 + 4/20 + 64/20 = 8.4, which exceeds 5.99, so the null hypothesis of an even distribution is rejected.
- 5
How is a Lorenz curve plotted and a Gini coefficient interpreted?
Model answer
Cumulative percentage of income is plotted against cumulative percentage of population, poorest first; the further the curve bows below the line of equality, the greater the inequality. The Gini coefficient is the area between the line and the curve divided by the whole area under the line, from 0 (equality) to 1.
- 6
How is a logarithmic scale read?
Model answer
Each major division represents a tenfold increase, so equal distances show equal ratios rather than equal amounts; a value halfway between 100 and 1,000 is about 316, not 550.
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