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What is a confidence interval?

Using the normal distribution, we can estimate a range of values which we expect to contain the mean. For example, if we take a sample of 30 students height, we can estimate the mean height of students in th...
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Answered by Alexander R. • Maths tutor
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Do global superpowers reflect the 'north-south' divide?

Global superpowers can be defined as states which are powerful on the global stage, both explicitly through their role in global institutions such as the UN and implicitly through their influence. Since the ...
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Answered by Phoebe R. • Geography tutor
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2-chloropropanoic acid has a Ka of 1.48E-3. Write an expression for Ka and hence or otherwise, calculate the pH of a 0.35M solution of 2-chloropropanoic acid

In these multiple part questions, it is often the case that the previous part of the question will provide necessary information for answering the following parts, as hinted by the use of 'hence'. It's very ...
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Answered by Colin M. • Chemistry tutor
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i) Simplify (2 * sqrt(7))^2 ii) Find the value of ((2 * sqrt(7))^2 + 8)/(3 + sqrt(7)) in the form m + n * sqrt(7) where n and m are integers.

i) (2 sqrt(7)) 2 = 2 2 sqrt(7) 2 = 4 * 7 = 28 (1 mark) ii) First of all substitute the answer from above. ((2 * sqrt(7)) 2 + 8) / (3 + sqrt(7)) = (28 + 8) / (3 + sqrt(7)) = 36 / (3 + sqrt(7)) Multiply by (3 ...
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Answered by Andrew B. • Maths tutor
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What is the difference between profit and cash flow?

Cash flow is all the money flowing in and out of a business. This is calculated at the exact time actual cash enters or leaves a business bank account or till. Profit is calcuated by calculating ALL transact...
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