We want to study the zinc concentration from a river. We have a sample of measurements...

We want to study the zinc concentration from a river. We have a sample of measurements taken in 25 diﬀerent locations in a river with sample mean x = 3 and population standard deviation σ = 0.3. The population is normally distributed.

1. Find the 95% and 99% conﬁdence intervals for the mean zinc concentration in the river.

2. Is the following statement correct? “If we repeat the same experiment multiple times and each time calculate the two conﬁdence intervals in question 1, then they cover x approximately 95% and 99% times respectively.” State your reason.

3. If we simply take x as the estimate for µ, how large a sample is required if we want to be 90% conﬁdent that the error will not exceed 0.05?

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orchestra answered 1 year ago

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