Final answer:
The sample proportion is the midpoint of the 80% confidence interval (0.12, 0.18), which is calculated as (0.12+0.18)/2, resulting in a sample proportion of 0.15. The correct answer is option D .
Step-by-step explanation:
When you are given an 80% confidence interval for a proportion, such as (0.12, 0.18), the sample proportion is the middle point of the interval. This is because a confidence interval is centered around the sample proportion, which is the best estimate of the true population proportion based on the sample data. To find the sample proportion, simply calculate the midpoint between the lower and upper bounds of the confidence interval.
To find the midpoint (sample proportion), add the lower bound to the upper bound and divide by 2:
Sample Proportion (p') = (Lower Bound + Upper Bound) / 2
Sample Proportion (p') = (0.12 + 0.18) / 2
Sample Proportion (p') = 0.30 / 2
Sample Proportion (p') = 0.15
Therefore, the sample proportion is 0.15, which corresponds to answer choice D.