AQA · Mathematics · 8300
GCSE Maths: Averages: mean (estimated)
Statistics · AQA GCSE Maths (8300). Cards are generated from the Corbettmaths textbook exercise, practice questions and answers for Averages: mean (estimated) (Corbettmaths Video 55), and every card links back to the exact page it came from. Practice tests are drawn from this deck’s own cards. Source material © Corbettmaths — used with attribution.
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How do you calculate the midpoint of a class interval?
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Add the lower and upper boundaries of the interval and divide by 2.
Why can't you calculate the exact mean from a grouped frequency table?
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Because you only know which interval each value falls in, not the exact individual values.
The formula for estimated mean from grouped data is: sum of (?) divided by total frequency.
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midpoint × frequency
When estimating the mean from grouped data, what assumption are you making about values within each interval?
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That all values in the interval can be represented by the midpoint value.
If you have class intervals with different widths, does the method for estimating mean change?
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No, you still find midpoints and use the same formula: sum(midpoint × frequency) ÷ total frequency.
When estimating the mean from grouped frequency data, what value represents each class interval?
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The midpoint of the class interval.
What is the formula for estimating the mean from a grouped frequency table?
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Sum of (midpoint × frequency) ÷ sum of frequencies, or Σfx ÷ Σf
In a grouped frequency table, what does the modal interval represent?
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The class interval with the highest frequency.
When might the mean not be the best average to represent a data set?
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When there are extreme values (outliers) that skew the mean, making it unrepresentative of typical values. The median or mode may be better in such cases.
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