True or False

1. A sampling strategy falls under the category of probability sampling if every unit in the population has a positive probability of getting selected in the sample.

2. In the presence of extreme outliers in data, the interquartile range is often considered a more appropriate measure of dispersion than the standard deviation.

3. In a normal distribution, a z-score of 2 corresponds to the 95th percentile.

4. The calculation Var(X+X) = Var(X) + Var(X) = 2 Var(X) is correct.