A Consumer Group Was Interested in Comparing the Operating Time

question 21

Multiple Choice

A consumer group was interested in comparing the operating time of cordless toothbrushes manufactured by two different companies. Group members took a random Sample of 18 toothbrushes from Company A and 15 from Company B. Each was charged Overnight and the number of hours of use before needing to be recharged was recorded. Company A toothbrushes operated for an average of 119.7 hours with a standard deviation Of 1.74 hours; Company B toothbrushes operated for an average of 120.6 hours with a Standard deviation of 1.72 hours. The 90% confidence interval is (-1.93, 0.13) . The correct Interpretation is

• A) We are 90% confident that, on average, there is no difference in operating hours Between toothbrushes from Company A compared to those from Company B.
• B) We are 90% confident that, on average, the toothbrushes from Company A operate Longer before needing to be recharged than the toothbrushes from Company B.
• C) We are 90% confident that, on average, the toothbrushes from Company B operate Longer before needing to be recharged than the toothbrushes from Company A.
• D) We are 90% confident that, on average, there is a difference in operating hours between Toothbrushes from Company A compared to those from Company B.
• E) None of the above.