Comprehensive Study Guide to the Edexcel Statistics Large Data Set (LDS)

Overview of the Edexcel Large Data Set (LES)

• Definition and Scope: The Edexcel Large Data Set (LDS) is a collection of weather data covering five locations within the United Kingdom and three locations situated abroad.

• Assessment Expectations:

  • Edexcel tests the student's knowledge and familiarity with the data set.

  • Students are not required to bring copies of the LDS into the examination.

  • Detailed memorization of actual data points within the set is not expected.

• Material Advantage: The specification states that questions based on the LDS are designed to provide a material advantage to students who have studied and are familiar with the data set.

• Question Characteristics:

  • Context and Terminology: Questions may assume familiarity with context and terminology without providing explicit explanations. This ensures that students who have not studied the data set do not have equal access to marks.

  • Data Usage: Questions may employ summary statistics, selected data points, or statistical diagrams derived from the LDS, which might be provided as stimulus material.

  • Sampling: Questions may be based on samples related to the LDS contexts to test the student's understanding of background context.

  • Complex Interpretation: Students may be required to interpret data in ways that would be considered too demanding if the context were entirely unfamiliar.

Temporal and Geographical Coverage

• Time Frames: The LDS contains data for two specific periods:

  • May to October 1987.

  • May to October 2015.

• United Kingdom Locations: There are five UK weather stations:

  1. Camborne

  2. Heathrow

  3. Hurn

  4. Leeming

  5. Leuchars

• Geographic Distribution and North-South Gradient:

  • Students must have a rough idea of the relative north-south positioning of these locations.

  • Leuchars is significantly further north than any other location and is coastal, which typically makes it colder than more southern locations like Hurn and Heathrow.

• Overseas Locations: There are three international weather stations:

  1. Jacksonville (Florida, USA)

  2. Beijing (China)

  3. Perth (Australia)

• The Great Storm of 1987: This major event occurred between October 15, 1987, and October 16, 1987. It was characterized by heavy rain, extremely high wind speeds, and widespread, devastating damage.

Large Data Set Variables and Measurement Standards

• Number of Variables: There are 11 distinct variables featured in the LDS.

• Missing Data: If a reading is unavailable, the entry is listed as ‘n/a’.

• Daily Mean Temperature:

  • Measured in degrees Celsius ($^{\circ}C$).

  • Values are recorded to one decimal place.

  • Negative values indicate temperatures below $0^{\circ}C$.

• Daily Total Rainfall:

  • Measured in millimetres ($mm$).

  • Special Notation: A value of ‘tr’ (trace) indicates a rainfall amount less than $0.05\,mm$.

  • Calculations: For mathematical calculations, a ‘tr’ value is treated as $0$.

• Daily Total Sunshine:

  • Measured in hours ($h$).

  • Values are recorded to one decimal place (e.g., an entry of ‘4.5’ equals four and a half hours).

• Daily Maximum Relative Humidity:

  • A measure of water vapour saturation in the atmosphere.

  • Measured as a percentage ($\%$).

  • Mist and Fog Threshold: Values exceeding $95\%$ are typically associated with mist and fog.

  • Saturation State: At $100\%$, the air is fully saturated, allowing condensation to occur.

• Daily Mean Windspeed:

  • Measured in knots ($\text{knots}$) in one column.

  • Conversion: $1\,\text{knot} = 1.15\,\text{mph}$.

  • Beaufort Scale: A separate column records windspeed using this non-numerical, empirical scale mapping values to descriptive terms: light, moderate, and fresh. "Light" is the most frequent occurrence in most locations.

• Daily Maximum Gust:

  • The maximum instantaneous speed recorded over a 24-hour period, measured in knots.

• Daily Mean Wind Direction:

  • Averaged over 24 hours.

  • Measured in degrees ($^{\circ}$) relative to true North; this signifies the direction the wind was blowing from.

  • Values are rounded to the nearest $10^{\circ}$. The corresponding cardinal direction is also provided.

• Daily Maximum Gust Direction:

  • The direction from which the wind was blowing during the hour the maximum gust occurred.

  • Measured in degrees relative to true North with corresponding cardinal directions.

• Cloud Cover:

  • Measured in oktas, which represent the fraction of the celestial dome covered by clouds.

  • Values range from $0$ (clear sky) to $8$ (complete overcast).

  • This is a discrete variable with 9 possible values.

• Visibility:

  • Measured horizontally in decametres ($dm$).

  • Conversion: $1\,dm = 10\,m$.

  • Missing data is indicated by a dash (—).

  • Typical range: $1000\,dm$ to $7000\,dm$.

  • Fog classification: Less than $100\,dm$.

  • Mist classification: Less than $200\,dm$.

• Pressure:

  • Measured in hectopascals ($hPa$) to the nearest whole number.

  • Readings are taken locally but converted into the equivalent sea-level pressure to eliminate altitude effects.

  • Values consistently hover around $1000\,hPa$.

  • High pressure is linked to good weather; low pressure is linked to rain, cold, and cloud cover.

Comparative Analysis of UK Weather Data (2015)

• Summary Table for UK Locations (approximate ranges):

• Location-Specific Insights:

  • Heathrow: Recorded the highest temperature. This is attributed to urban heat absorption by airport buildings and black asphalt runways.

  • Outliers in Heathrow Rainfall: Heathrow shows an extreme rainfall range. On August 26, 2015, a value of $51.6\,mm$ was recorded. The next highest value was $37.6\,mm$, after which values drop to $19\,mm$, suggesting at least two statistical outliers.

  • Leuchars Windspeed: Features higher windspeed values, attributed to its close proximity to the sea.

  • Temperature Latitudinal Trends: Leuchars and Leeming exhibit the lowest temperatures because they are located significantly further north than the other UK stations.

Comparative Analysis of Overseas Weather Data (2015)

• Restricted Variables: Overseas data sets are less comprehensive, providing only daily average temperature, daily rainfall, daily mean pressure, and daily mean windspeed (both in knots and the Beaufort scale).

• Summary Table for Overseas Locations (approximate ranges):

• Jacksonville (USA):

  • Located in Florida in the Northern Hemisphere, close to the coast.

  • Characterized by high temperatures and intense rainfall.

  • Rainfall totals are higher than the UK due to being closer to the equator and hurricane formation zones. Jacksonville's rainfall is more intense, whereas UK rainfall is more spread out.

  • Dry periods: Jacksonville had $102$ days without rainfall between May 1 and October 31, 2015.

  • Windspeeds are generally moderate.

• Beijing (China):

  • Located in the Northern Hemisphere.

  • Displays high temperatures similar to Jacksonville but experiences lower lows due to monsoon circulation.

  • Monsoon Mechanism: Cold currents from the North West prevail in winter; these are replaced by hot, humid currents from the tropics during summer. This circulation brings periods of intense summer rainfall.

  • Dry periods: Beijing recorded $115$ days without rain between May 1 and October 31, 2015.

• Perth (Australia):

  • Located in the Southern Hemisphere, meaning seasons are reversed (June through August is winter).

  • Coastal location results in expected higher windspeeds.

  • Outliers in Perth Rainfall: Recorded two exceptionally high values of $63\,mm$ and $102\,mm$. If these are excluded, the rainfall range would be reduced significantly to $0 - 38\,mm$.