Question 1

What is the difference between discrete and continuous data?

Accepted Answer

Discrete data can only take specific values (usually integers), like the number of students in a class or shoe sizes. Continuous data can take any value within a range, like height, weight, or temperature. This distinction matters because it affects which graphs and summary statistics are appropriate. For example, histograms are used for continuous data, while bar charts are for discrete data.

Question 2

How do I calculate the interquartile range (IQR) from a cumulative frequency graph?

Accepted Answer

To find the IQR from a cumulative frequency graph, first locate the lower quartile (Q1) at the 25th percentile and the upper quartile (Q3) at the 75th percentile on the cumulative frequency axis. Then read across to the data values on the x-axis. The IQR is Q3 minus Q1. This method works because the cumulative frequency graph shows the running total of frequencies, allowing you to find percentiles directly.

Question 3

What is the Large Data Set (LDS) and how do I use it in the exam?

Accepted Answer

The Large Data Set (LDS) is a specific dataset provided by AQA, typically containing weather data from UK weather stations. You are expected to be familiar with its variables (e.g., temperature, rainfall, wind speed) and be able to apply statistical techniques like calculating means, drawing scatter diagrams, and interpreting trends. In the exam, questions may ask you to comment on patterns or anomalies in the LDS, so practice exploring it beforehand.

Question 4

When should I use a histogram instead of a bar chart?

Accepted Answer

Use a histogram for continuous data that has been grouped into class intervals (e.g., heights 150-160 cm). The bars touch each other to indicate continuity. Use a bar chart for discrete or categorical data (e.g., favourite colour or number of siblings), where bars are separated by gaps. In a histogram, the area of each bar represents frequency, so the vertical axis is frequency density, not frequency.

Question 5

How do I choose the best sampling method for a given scenario?

Accepted Answer

The best sampling method depends on the population and resources. Simple random sampling gives every member an equal chance but requires a complete list (sampling frame). Stratified sampling ensures subgroups are represented proportionally, useful when the population has distinct layers (e.g., year groups). Systematic sampling is easy to implement but can introduce bias if there's a pattern. Quota sampling is non-random and quicker but may be biased. Opportunity sampling uses whoever is available but is highly biased. In exams, justify your choice based on practicality, cost, and bias.

Question 6

What is the difference between variance and standard deviation?

Accepted Answer

Variance is the average of the squared differences from the mean, while standard deviation is the square root of variance. Standard deviation is in the same units as the original data, making it easier to interpret. For example, if data is in cm, variance is in cm², but standard deviation is in cm. Both measure spread, but standard deviation is more commonly used in reporting because it's more intuitive.

Use of data in statistics

Assessment criteria

Topic Overview

Key Concepts

What You Need to Demonstrate

Assessment Criteria

Assessment Guidance

Common Mistakes

Frequently Asked Questions

Before You Start

Key Terminology

Ready to learn?

Related Topics in AQA vocational Mathematics

A: Proof

B: Algebra and functions

C: Coordinate geometry in the ( x , y ) plane

D: Sequences and series

How to Revise Use of data in statistics — AQA A-Level Mathematics

Examiner Tips for Use of data in statistics

Common Mistakes in Use of data in statistics

Key Marking Points