Wood cutter. A wood cutter manufacture claims that their new machine can have the speed of 45 meter per second for the hardest wood species and has less variation.

This record shows faster speed than their old wood cutter machine. To justify this, a sample of 10 different hardest wood species were cut by using the new and the old cutter.

The results showed that the mean speed for the new cutter was 46 meter per second and for the old cutter was 50 meter per second. The standard deviations were 1.83 meter per second and 2.16 meter per second, respectively.

a) By using the provided data, a two-sample t 95% confidence interval for the difference between the two means as

(-6.2886, -1.7114) was computed. What conclusion would be reached based on the result?

b) Is this procedure appropriate? What assumption, if any, is violated?

c) What may have impacted the results in this analysis?