Collecting Data

Types of Data

Two-Way Tables

Frequency Trees

Designing Questionnaires

Stratified Sampling

Two-Way Tables and Frequency Trees

Prerequisite Knowledge

• Interpret and construct statistical diagrams for discrete and continuous data and know their appropriate use.
• interpret, analyse and compare the distributions of data sets from univariate empirical distributions through:
  • appropriate graphical representation involving discrete, continuous and grouped data
  • appropriate measures of central tendency (median, mean, mode and modal class) and spread

Success Criteria

• Infer properties of populations or distributions from a sample, whilst knowing the limitations of sampling.
• apply statistics to describe a population
• Interpret, analyse and compare the distributions of data sets from univariate empirical distributions through appropriate graphical representation involving discrete, continuous and grouped data.

Key Concepts

• Students need to understand the benefits of using two-way tables as a means to exhaustively cover each outcome for multiple events and use them to calculate probabilities.
• When designing questionnaires students need to consider time periods, multiple check boxes which do not overlap and the need to collect a wide ranging sample to reduce bias.
• It is important to recognise the different statistical techniques that are used to analyse and represent qualitative, quantitative, discrete and continuous data.

Common Misconceptions

• Students often have difficulty designing two-way tables.
• When designing questionnaires common errors include:
  • No time period
  • Overlapping responses
  • Lack of ‘none’ or ‘other’ option.
  • Check boxes with unequal widths.
  • Double negative questions.
• Students often try to represent continuous data using methods that are only applicable for discrete sets.