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Basic Statistics

Maths: Edexcel IGCSE Higher, topic 6.1.1

Statistics Basics

Statistics can be used to describe a population.

Mode

Mode

  • The mode is the most common value.
  • There may be more than one mode.
Median

Median

  • The median is the middle value when the values are ordered by size.
  • If there are two middle numbers then the median is the average of these two values.
Mean

Mean

  • The mean is the sum of all the values divided by the number of items.
Range

Range

  • The range is the difference between the highest and lowest value.

Statistics Basics

Quartiles

Quartiles

  • The lower quartile, median and upper quartile are the values 25%, 50% and 75% through the dataset.
  • They are written as Q1, Q2, Q3.
Interquartile range

Interquartile range

  • The interquartile range is Q3 - Q1, the difference between the upper and lower quartile.
  • It is a measure of spread, like the range, and is less affected by outliers.
Outliers

Outliers

  • Outliers are data values that don’t fit in the same pattern as the rest of the data.

Test yourself on Basic Statistics

  • Here is a list of numbers: 1, 4, 6, 7, 9, 11, 11
    What is the mode?

  • Here is a list of numbers: 5, 5, 5, 7, 10, 12, 14, 14
    What is the mode?

  • Here is a list of numbers: 1, 4, 6, 7, 9, 11, 11
    What is the median?

  • Here is a list of ages of people in a classroom: 8, 8, 9, 8, 63, 8, 9, 9, 8, 9, 9, 8.
    Which one is the outlier?

  • Which of these is more affected by outliers?

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