Standard Deviation and Normal Distribution

In a normal distribution, approximately what percentage of data falls within 2 standard deviations from the mean?

A screening program in Mumbai measured hemoglobin (Hb) levels in 500 healthy non-pregnant women aged 18–45 years. The mean Hb was 13 g/dL with a standard deviation of 1.5 g/dL. The program defines anemia as Hb < 12 g/dL. Assuming normal distribution, which of the following best represents the z-score for an Hb of 12 g/dL, and what does this indicate?

A public health researcher in Delhi conducted a cross-sectional survey measuring systolic blood pressure (SBP) in 1000 randomly selected adults aged 40–60 years. The mean SBP was 130 mmHg with a standard deviation of 15 mmHg. Assuming the distribution is normal, approximately what percentage of the population is expected to have SBP between 100 and 160 mmHg?