1. **Problem statement:** We are given the mean ($\mu$) and standard deviation ($\sigma$) for systolic blood pressure in non-smoking females aged 18-35 years. The mean is 120 mmHg and the standard deviation is 5 mmHg. We need to fill in the missing numbers on the horizontal axis of a normal distribution curve at positions $-2\sigma$, $-\sigma$, $\mu$, $\sigma$, and $2\sigma$. 2. **Formula and explanation:** For a normal distribution, the values at these positions are calculated as: $$ \text{Value at } -2\sigma = \mu - 2\sigma $$ $$ \text{Value at } -\sigma = \mu - \sigma $$ $$ \text{Value at } \mu = \mu $$ $$ \text{Value at } \sigma = \mu + \sigma $$ $$ \text{Value at } 2\sigma = \mu + 2\sigma $$ 3. **Calculations:** - At $-2\sigma$: $120 - 2(5) = 120 - 10 = 110$ - At $-\sigma$: $120 - 5 = 115$ - At $\mu$: $120$ - At $\sigma$: $120 + 5 = 125$ - At $2\sigma$: $120 + 2(5) = 120 + 10 = 130$ 4. **Interpretation:** These values mark the positions on the horizontal axis of the normal distribution curve for systolic pressure. They help us understand the spread of blood pressure values around the mean. **Final answer:** The missing numbers on the horizontal axis are 110 at $-2\sigma$, 115 at $-\sigma$, 120 at $\mu$, 125 at $\sigma$, and 130 at $2\sigma$.