Desert System Skills (AQA A Level Geography)

Hot Desert Skills

Short answer questions

• These questions only assess knowledge (AO1) and carry 4 marks each

• Four clear statements are needed (not always sentences) that answer the question and shows knowledge of the topic

• Examples or details are useful but not always needed

• Take no longer than 5 minutes to answer these questions

Climate graphs

• Climate graphs show average rainfall and temperatures typically experienced in a particular location

• Temperature is shown on a line graph, and rainfall on a bar graph

• They are usually represented on the same set of axes with the months of the year along the base

Interpreting and describing climate graphs

• Look at the overall shape of the graph

  • Is the temperature line steep or gentle?

  • Does it change throughout the year or look almost flat?

• Look for extremes

  • Quote the highest and lowest temperature and rainfall and the month in which it occurs

  • Remember to quote units, eg celsius or millimetres

  • Identify the seasons when most or least rain falls

  • Or when the highest and lowest temperatures are experienced

• Work out the temperature range by subtracting the lowest figure from the highest figure

• Add the rainfall totals for each month together to work out the total annual rainfall

Data response questions

• All carry 6 marks and assess skills (AO3)

• 'Analyse' is the frequent command word

• Knowledge development is not needed to explain the data and will not gain credit (just waste time)

• Simple or obvious statements will gain minimum marks

• Always look for patterns/trends/ranges

• Identify anomalies or countertrends

• Re-work the data - find percentages, mean, averages, range etc. 

• Use qualitative descriptive words - do not just copy from the resource

• Make connections and draw relationships between different sets of data provided (compare and contrast)

• Question or critique the data relationship or the data itself

• Take no longer than 9 minutes to answer these questions

Data stimulus questions

• Carry either 6 or 9 marks and assesses topic knowledge and ability to apply that knowledge to other situations (AO1 and AO2)

• Question will usually ask for 'own knowledge' as well as a general understanding of the resource

• Refer to the data provided, but also use the resource as an access route to demonstrate your own knowledge and understanding and how it applies to the wider concept of the resource

• Use the same approach for data response and be prepared to make a judgement (assess)

• Take no longer than 9 minutes for 6 marks or 12 minutes for 9 marks

Scatter graph

• Points should not be connected

• The best-fit line can be added to show the relations

• Used to show the relationship between two variables

  • In a river study, they are used to show the relationship between different river characteristics such as the relationship between the width and depth of the river channel

Types of correlation

• Positive correlation

  • As one variable increases, so too does the other

  • The line of best fit goes from the bottom left to the top right of the graph

• Negative correlation 

  • As one variable increases the other decreases

  • The line of best fit goes from the top left to the bottom right of the graph

• No correlation

  • Data points will have a scattered distribution

  • There is no relationship between the variables

Percentage and percentage change

• To give the amount A as a percentage of sample B, divide A by B and multiply by 100

  • In 2020, 25 out of 360 homes in Catland were burgles. What is the percentage (to the nearest whole number) of homes burgled?

  • 

• A percentage change shows by how much something has either increased or decreased

• 

  • In 2021 only 21 houses were burgled. What is the percentage change in Catland?

  • 

  • There has been a decrease of 16% in the rate of burglaries in the Catland area

• Do remember that a positive figure shows an increase but a negative is a decrease

Statistical Skills

• This is the study and handling of data, which includes ways of gathering, reviewing, analysing, and drawing conclusions from data

Percentage and percentage change

• To give the amount A as a percentage of sample B, divide A by B and multiply by 100

  • In 2020, 25 out of 360 homes in Catland were burgles. What is the percentage (to the nearest whole number) of homes burgled?

  • 

• A percentage change shows by how much something has either increased or decreased

• 

  • In 2021 only 21 houses were burgled. What is the percentage change in Catland?

  • 

  • There has been a decrease of 16% in the rate of burglaries in the Catland area

• Remember that a positive figure shows an increase but a negative is a decrease

Mean, median, mode and range

• Mean = average value (all the values added and divided by the number of items)

• Median = middle value when ordered in size

• Mode = most common value

• Range = difference between the highest value and lowest value

• Taking the example above to calculate:

• Mean -

• Median - reordering by size =  = 95 is the middle value

• Mode - only 64 appears more than once

• Range -

Upper, lower and interquartile range

• These are the values of a quarter (25%) [lower quartile (LQ)] and three-quarters (75%) [upper (UQ)] of the ordered data

• The interquartile range (IQR) is the difference between the upper (UQ) and lower quartile (LQ)

• It measures the spread (dispersion) of data around the median

• A large number shows the numbers are fairly spread, whereas, a small number shows the data is close to the median

• UQ - LQ = IQ []

Standard deviation

• This measures dispersion more reliably than IQR and the symbol for it is 'σ' (sigma)

• The formula is  

• Σ means 'sum of' and  is another way of writing 'mean' and 'n' is the number of samples taken

• Work out individual aspects of the formula first e.g. the mean

• Sample results:

1. Calculate the mean - 

2. Calculate  for each number

3. Square each of those values (the square of a negative number becomes positive)

4. Add the squared values to give 

5. Divide the total by 'n'

6. Finally, find the square root

• 

• Numbers closely grouped around the mean shows a small deviation

• A large standard deviation would show a set of numbers that were spread out

Spearman's rank correlation coefficient

• A test to determine if two sets of numbers have a relationship

• Not the easiest to calculate

• Σ means 'sum of',   is the difference and 'n' is the number of samples taken

• The formula is 

1. Rank each number in both sets of data, with the highest number given rank 1, second highest 2 etc.

2. Calculate 'd' which is the difference between ranks of each group e.g. ranks for group 5 are 4 and 6; difference will be 2

3. Square value 'd' and calculate the total  to find 

4. Finally, calculate the coefficient of  using the above formula

5. The resulting number should always be between -1 and +1

GNP ($) per capita and Life Expectancy (years)

• . 

• rs =1 -6 ×14123 - 12 = 1- 841716 =1-0.048951 (0.05) = 0.95

• (0.048951 can be rounded to 2 decimal places giving 0.05)

• A positive result shows a positive correlation, where one variable increases so does the other

• The closer the number is to 1, the stronger the positive correlation

• A negative results shows a negative correlation, where one variable increases the other decreases

• The closer the number is to -1 the stronger the negative correlation

• If however, the correlation is 0 or near to 0, there is no relationship

Determining significance

• Spearman's rank may show that two sets of numbers are correlated, however, it does not show how significant the link between the two values are

• To check for significance; a table of critical values or a graph is needed

• This looks at the probability of the links occurring by chance 

• A 5% or higher probability of chance is not significant evidence for a link

• 1% or less is a significant evidence of a link

• This is the significance level of a statistical test

• The degrees of freedom needs calculating - n-2   

  • Using the example above:  12 - 2 = 10 degrees of freedom

  • As rs = 0.95 then the correlation has a less than 1% probability of being by chance

  • Therefore, there is a high significance level of a relationship between GNP and life expectancy

  Spearman’s Rank Correlation Significance Table