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# S2 question help needed watch

1. How do you do q3 a)? When does the (x-5) affect the variance or mean?

Thanks.
2. Note that the variance of a quantity is defined as the mean of the square minus the square of the mean. It is also equal to the mean of the squared deviation from the mean, which is basically ∑(x - u)^2/n, where u is the mean and n is the number of xs you have (20 in this case because you took twenty measurements). The variance is a way of measuring how far away a given quantity is from the mean. The mean is a way of measuring the "average" value so basically the value around which everything gravitates. It is defined as the sum of all quantities ∑x, divided by the number of quantities, n. What can you intuitively say about effect of adding or subtracting a constant from all your x-values on the mean and the variance? Can you show it mathematically based on their definitions? If you show the effect of subtracting a value on the mean and variance you should be able to find the variance using the first definition of the variance I gave above.
3. (Original post by JulieEdiz)

How do you do q3 a)? When does the (x-5) affect the variance or mean?

Thanks.
If there is a section on "coding" in your textbook, that would be a good place to look for worked examples of this kind of thing.

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