An Article That Appeared in the British Medical Journal (2010)

Multiple Choice

An article that appeared in the British Medical Journal (2010) presented the results of a randomized experiment conducted by researcher Jeremy Groves, whose objective was to determine whether the weight of his bicycle could affect his travel time to work. On each of 56 days (from mid-January to mid-July 2010) , Groves tossed a £1 coin to decide whether he would be biking to work on his carbon frame (lighter) bicycle that weighed 20.9 lbs or on his steel frame (heavier) bicycle that weighed 29.75 lbs. He then recorded the commute time (in minutes) for each trip.
Here are the summary statistics for his data:
-A 95% confidence interval for the difference in long-run mean commute time between frames (Carbon - Steel) is (-2.39, 3.45) min. How would you interpret this interval?

A) We are 95% confident that commute times are, on average, between 2.39 min faster to 3.45 min slower for carbon frames compared to steel frames.
B) We are 95% confident that commute times are, on average, between 2.39 min slower to 3.45 min faster for carbon frames compared to steel frames.
C) In 95% of all commutes, the carbon frame will be between 2.39 min faster to 3.45 min slower than the steel frame.
D) In 95% of all commutes, the carbon frame will be between 2.39 min slower to 3.45 min faster than the steel frame.