IP2U15 HOT Q2
IP2U15 HOT Q2
Secondary 4
\(16\) pupils sat for a test. The sum of their marks is \(504\). The sum of the squares of their marks is \(16855\).
- Calculate
- the mean,
- the standard deviation, of these test marks.
- One of the marks was \(43\) but was incorrectly recorded as \(25\). Calculate the correct mean and standard deviation of these test marks.
- Explain, stating your reasons clearly,
- why the mean has increased,
- why the standard deviation has increased.
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Answer:(a)(i) \(31.5\). (ii) \(7.82\) (3 s.f.). (b) Mean \(32.625\), standard deviation \(8.10\) (3 s.f.). (c) Both increase; see working.
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