Answer:
b. The margin of error would decrease.
Step-by-step explanation:
Margin of error of a confidence interval:
The margin of error of a confidence interval has the following format:
In which z is related to the confidence level, is the standard deviation of the population and n is the size of the sample.
This means that the margin of error is inversely proportional to the size of the sample, which means that if the sample size increases, the margin of error decreases.
In this question, the sample size is increased, leading to a smaller margin of error. So the correct answer is given by option b.