Statistics · Module 9
Answers and explanations · Decide whether a difference matters and whether the comparison is fair
Compare these references after your own attempt. You can read them at any time; they do not record a live model or vendor run.
Statistics · Module 9
Compare these references after your own attempt. You can read them at any time; they do not record a live model or vendor run.
9A. Absolute change=9%−12%=−3 percentage points. Relative change=(9−12)/12=−0.25=−25%. “Down 3%” could mean 3 percentage points or 3% of the baseline, which would be a much smaller change. Write the units and the baseline.
9B. At 80% short and 20% long, A=0.8×90%+0.2×10%=74%; B=0.8×95%+0.2×20%=80%. The equal-mixture rates were 50% and 57.5%. Both targets favor B, but the absolute rates and differences change because the target route mix changes. Standardization is a descriptive comparison for the specified mixture; it does not automatically identify a causal hub effect.
9C. The interval excludes zero and lies on the lower-duration side. It does not establish a reduction of at least 2 minutes because it includes −0.55, which corresponds to a smaller benefit. A real controlled pilot with a stated practical threshold, cost/quality measures and an appropriate design is more defensible than claiming a full rollout is proven worthwhile by simulated data.