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The standard deviation of n numbers $$x_{1}$$, $$x_{2}$$, $$x_{3}$$,......, $$x_{n}$$, with mean x is equal to $$\sqrt{\frac{s}{n}}$$, where S is the sum of the squared differences, $$(x_{i} - x)^{2}$$ for 1 ≤ i ≤ n.

In a set of data, 1 appears k times, 5 appears k times, and 3 appears once. What is the minimum k to make the standard deviation greater than 1.95 ?

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