Question

An team of engineers is preparing a report on the battery lifetime of a new cell phone battery they have designed. At a 95% confidence level, they estimated that their battery's mean lifetime was 3.2 ±1.0 days based on a sample of 30. They want to adjust their findings so the margin of error is as small as possible.

Which of the following will produce a lower margin of error?

1. Increase the confidence level to 99%.
2. Increase the sample size to 60 batteries.
3. Decrease the sample size to 25 batteries.
4. Decrease the confidence level to 90%.

• A. 1, 2 and 3

• B. 1 and 3

• C. 2 and 4

• D. 4 only

• E. 1, 2, 3 and 4

Answer 1