Estimate with 95% confidence the difference between the average distances driven before worn-out by cars fitted with the new steel-belted radial tyres and those fitted with the existing model. Assume that the two population distances are normally distributed.

New 57 64 102 62 81 87 61 62 74 62 100 90 83 84 86 62 67 40 71

Exst 48 50 89 56 78 75 50 49 70 66 98 86 78 90 98 58 58 41 61