Question

Researchers studying the sticky droplets found on spider webs will measure the widths of a random sample of droplets. From the sample, the researchers will construct a 95 percent confidence interval to estimate the mean width of all such droplets. Which of the following statements about a 95 percent confidence interval for the mean width is correct?
A. The interval will be narrower if the researchers increase the level of confidence to 99 percent.
B. The interval will be narrower if the researchers increase the sample size of droplets.
C. The interval will be wider if the researchers decrease the level of confidence to 90 percent.
D. The interval will be wider if the researchers increase the sample size of droplets.
E. The width of the interval will not be affected if the researchers increase or decrease the number of droplets in the sample.

Answer 1

Answer:

B. The interval will be narrower if the researchers increase the sample size of droplets.

Step-by-step explanation:

Margin of error of a confidence interval:

The higher the margin of error, the wider an interval is.

$M = z\frac{\sigma}{\sqrt{n}}$

In which z is related to the confidence level(the higher the confidence level, the higher z), $\sigma$ is the standard deviation of the population and n is the size of the sample.

From this, we conclude that:

If we increase the confidence level, the interval will be wider.

If we increase the sample size, the interval will be narrower.

Which of the following statements about a 95 percent confidence interval for the mean width is correct?

Increasing the sample size leads to a narrower interval, so the correct answer is given by option B.