Topic Details (Notes format)

How to Calculate Variance and Standard Deviation

Subject: Mathematics

Book: Maths Mastery

Variance measures how spread out data values are around the mean, calculated by averaging the squared differences from the mean. Standard deviation is the square root of variance, returning the measure to the original data units. For a dataset [2, 4, 4, 6, 8], the mean is 4.8, each difference is (2 – 4.8)², (4 – 4.8)², etc., then averaged to get variance, and the square root yields the standard deviation. Higher standard deviation indicates greater spread. These metrics are fundamental in statistics, quality control, finance risk, and any field requiring data analysis. Familiarity with variance and standard deviation fosters statistical literacy and well-informed decisions.

Practice Questions

The ratio of two numbers is 3:5, and their sum is 64. What are the numbers?

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If 2x = 16, what is the value of x?

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If the length of a rectangle is doubled and the width is halved, what is the change in area?

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If 2x - 3 = 7, what is the value of x?

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The sides of a triangle are 5 cm, 12 cm, and 13 cm. What type of triangle is it?

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If a = 4 and b = 5, what is the value of (a+b)^2?

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The sides of a triangle are 7, 24, and 25. Is this a right triangle?

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If a square has a perimeter of 64 cm, what is its area?

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If a + b = 10 and ab = 21, what is the value of a^2 + b^2?

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If sin(A) = 3/5 and cos(B) = 5/13, where A and B are acute angles, what is sin(A+B)?

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