Question

Which estimator will consistently have an approximately normal distribution? a.Proportion b.Median c.Standard d.Deviation range

Answer 1

Estimator is the rule for calculating estimation. 
The normal distribution is the most important and most widely used distribution in statistics.
The normal curve is symmetrical about the mean μ;The mean is at the middle and divides the area into halves;The total area under the curve is equal to 1;The Normal (Gaussian) distribution is completely determined by its mean and standard deviation σ (or variance σ2). 
The median estimator has an approximately normal distribution.