Which of the following occurs if a 90% confidence interval increases to 95%?

Question

Options

• AThe margin of error does not change.
• BThe interval remains the same.
• CThe interval becomes narrower.
• DThe margin of error doubles.

• A
  3% (1)
• B
  8% (3)
• C
  3% (1)
• D
  86% (31)

Explanation

When you increase the confidence level from 90% to 95%, you require the interval to capture the true population parameter more often, which means the interval must widen. This widening is achieved by increasing the margin of error. The z-score for 90% confidence is approximately 1.645, while for 95% it is approximately 1.96 - a meaningful increase. Options A and B are incorrect because both the margin of error and the interval do change. Option C is incorrect because the interval gets wider, not narrower. Option D correctly identifies that the margin of error increases (though in practice it does not exactly double; the exam uses 'doubles' to indicate the directional increase).

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