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Statistics

Quick questions on Data presentation and interpretation: averages, spread, outliers and correlation - OCR A-Level Maths A

4short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What are outliers?
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An outlier is a value far from the rest. Two common rules are: more than 1.5×IQR1.5 \times \text{IQR} beyond a quartile, or more than two standard deviations from the mean. The question states which rule to use.
What are comparing two distributions?
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To compare data sets, always compare a measure of location and a measure of spread, in context. For example "the median mark of class A (62) is higher than class B (55), and class A's smaller interquartile range (10 versus 18) shows its marks were more consistent."
What is q1?
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A class width is 55 and the frequency is 3030. Find the frequency density. [1 mark]
What is q2?
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Data has mean 5050 and standard deviation 44. Using the two-standard-deviation rule, find the upper outlier boundary. [2 marks]

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