1. **State the problem:** We need to find the standard deviation of the number of cell phones sold from Monday to Friday, given the data: 20, 21, 22, 30, 32. 2. **Formula for standard deviation:** The standard deviation $\sigma$ for a sample is given by: $$\sigma = \sqrt{\frac{1}{n-1} \sum_{i=1}^n (x_i - \bar{x})^2}$$ where $n$ is the number of data points, $x_i$ are the data values, and $\bar{x}$ is the mean. 3. **Calculate the mean $\bar{x}$:** $$\bar{x} = \frac{20 + 21 + 22 + 30 + 32}{5} = \frac{125}{5} = 25$$ 4. **Calculate each squared deviation:** $$ (20 - 25)^2 = (-5)^2 = 25 $$ $$ (21 - 25)^2 = (-4)^2 = 16 $$ $$ (22 - 25)^2 = (-3)^2 = 9 $$ $$ (30 - 25)^2 = 5^2 = 25 $$ $$ (32 - 25)^2 = 7^2 = 49 $$ 5. **Sum of squared deviations:** $$ 25 + 16 + 9 + 25 + 49 = 124 $$ 6. **Calculate variance:** $$ s^2 = \frac{124}{5 - 1} = \frac{124}{4} $$ Show cancellation: $$ s^2 = \frac{\cancel{124}}{\cancel{4}} = 31 $$ 7. **Calculate standard deviation:** $$ \sigma = \sqrt{31} \approx 5.57 $$ **Final answer:** The standard deviation of the number of cell phones sold is approximately **5.57**.