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Mathematics and Statistics Skills

Statistical skills: averages, spread, percentages and correlation

  • 3 things to know
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Overview

Mean, median, mode and modal class, range and interquartile range, running totals of frequencies, percentage increase and decrease, percentiles, bivariate data, lines of best fit, rising and falling relationships, prediction, interpolation and extrapolation.

What you need to know

Answer each one before you reveal it.

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Key term

How are the mean, mode, modal class and range of a data set found, given depths from 0.4 m to 1.6 m?

Key term

What is the mean, and how is it worked out?

Key term

What is the mode?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the mean, and how is it worked out?

    Model answer

    The arithmetic average, found by adding every value together and dividing the total by how many values there are.

  2. 2

    What is the median, and how do you find it when there is an even number of values?

    Model answer

    The middle value once the figures are put in order; with an even number you take the mean of the two central values.

  3. 3

    Why is the middle value often preferred to the mean when one reading is extreme?

    Model answer

    Because a single very large or very small figure drags the mean away from what is typical, while the middle value barely shifts.

  4. 4

    What is the mode?

    Model answer

    The value that appears more often than any other in the set.

  5. 5

    What is the modal class?

    Model answer

    The group holding more readings than any other, once the data has been sorted into classes.

  6. 6

    Eight river depths are recorded, the shallowest 0.4 m and the deepest 1.6 m. What is the range?

    Model answer

    1.2 m, found by subtracting the smallest value from the largest.

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