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What is meant by a confidence level of $90\%$?
There are $90$ chances out of $100$ that the sample results will not vary from the true characteristics of the population by more than a specified amount.
The point estimate is within $10\%$ of the true population value.
The expected error rate is equal to $5\%$.
A larger sample size is required than if the desired confidence level were equal to $95\%$.