Final answer:
The confidence interval 0.231±0.089 can be expressed as [0.142, 0.320] in interval form.
Step-by-step explanation:
The confidence interval 0.231±0.089 can be expressed in interval form as [0.142, 0.320]. To calculate this, you subtract and add the margin of error from the mean value. In this case, the mean is 0.231 and the margin of error is 0.089, so the lower endpoint of the interval is 0.231 - 0.089 = 0.142 and the upper endpoint is 0.231 + 0.089 = 0.320.