If the confidence level increases, what happens to the interval width?

• A. It becomes wider.
• B. It becomes narrower.
• C. It stays the same.
• D. It disappears.

Answer: (A)

Raising the confidence level means you want more assurance that the interval contains the true parameter, so you widen the margin of error. The critical value from the distribution increases with higher confidence, which makes the interval wider. For example, going from 95% to 99% confidence uses a larger cutoff, expanding the range you must cover to ensure the true value is included. This reflects the trade-off: higher confidence sacrifices precision for greater certainty. The interval does not stay the same, nor does it disappear; it simply becomes wider.