Sample mean is always:
The lower endpoint of the 99% confidence interval. 

The middle of the confidence 99% interval. 

The upper endpoint of the 99% confidence interval. 
The average monthly electricity consumption in a random sample of 100 households in February 2016 in North Kingstown was 637 kilowatt hours (kWh) with sample standard deviation s=45kwh. A 95% confidence interval for the true electricity consumption in North Kingstown is
637 ± 1.95 * 45/10 

637 ± 1.96 * 45 

637 ± 1.96 * 45/10 

637 ± 1.96 * 45/200 
We take two samples of sample sizes n1=10 and n2=100 from a normal population with the same mean and sd. We compute a 95% confidence interval for each of the samples. The 95% CI obtained from the second sample (with n2=100) is wider than 95% CI obtained for the first sample (with n1=10).
True  
False 
The general formula of a confidence interval for the sample statistics (e.g., mean) is
standard error ± multiplier* point estimate 

standard estimate ± multiplier* point error 

point estimate ± multiplier*standard error 
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