Final answer:
Decreasing the sample size leads to an increase in the margin of error, resulting in a wider confidence interval and less precision in estimating the population parameter.
Step-by-step explanation:
Decreasing the sample size affects the margin of error by making the confidence interval wider. This occurs because a smaller sample size tends to increase variability, which in turn requires a larger interval to capture the true population parameter with the same level of confidence. When conducting a poll or study, if we want to decrease the margin of error, we would typically need to increase the sample size.
The margin of error informs us how close the poll results are to the actual opinion or parameter being measured. A larger sample size generally leads to a lower margin of error, which is desirable because it gives a more precise estimate of the population parameter. Conversely, decreasing the sample size would increase the margin of error, indicating less precision and reliability in the estimates provided by the sample.