AQA GSCE: Section B - Statistics

Qualitative Data

Data that describes qualities or characteristics; not numerical and often collected using words or categories.

Quantitative Data

Data that involves numbers and quantities; can be measured or counted and allows calculations like mean and median.

Discrete Data

Data that can only take on certain values, usually whole numbers, and has gaps between values.

Continuous Data

Data that can take any value within a range, with no gaps, allowing decimals or fractions.

Primary Data

Data collected firsthand by the investigator, making it more reliable and specific for the research purpose.

Secondary Data

Data that has been collected by someone else for a different purpose; quicker to access but may be less specific or outdated.

Random Sampling

A sampling method where everyone in the population has an equal chance of being chosen, ensuring unbiased results.

Stratified Sampling

A sampling method where the population is divided into groups, and a sample is taken in proportion to the size of each group.

Bias in Data Collection

When data collected does not fairly represent the population, often due to leading questions or specific group sampling.

Reliability

The degree to which data is consistent and repeatable; similar results should be obtained if the data collection process is replicated.

Validity

The relevance of data and its ability to measure what it is supposed to; useful for answering the research question.

Bar Charts

Graphs used to show discrete data, with separate bars representing categories and height indicating frequency.

Pie Charts

Graphs that represent data as proportions of a circle, with sectors showing fractions or percentages of the total.

Mean

The average value calculated by adding all values and dividing by the number of values.

Median

The middle value of a data set when ordered; if even, it is the mean of the two middle numbers.

Mode

The value that appears most frequently in a data set; there can be no mode, one mode, or multiple modes (bimodal).

Range

The difference between the highest and lowest values in a data set.

Interquartile Range (IQR)

A measure of the spread of the middle 50% of the data, calculated as Q3 (upper quartile) - Q1 (lower quartile).

Cumulative Frequency Graphs

Graphs used to estimate medians, quartiles, and percentiles, plotting upper class boundaries against cumulative frequency.

Box Plots

Graphs that display five key values (minimum, lower quartile, median, upper quartile, maximum) to compare data distributions.