enter image description here I would really be grateful if someone could let me know how to answer Part (a) of Question 1. I believe i should scatter plot both x and y values separately for year 2000 and year 2001 on same graph and prove that there is a change.

am I doing it right or wrong?

  1. I am really blank for part c.

Thank you in advance. Will greatly appreciate prompt response.

  • $\begingroup$ For c) does he expect that you write down the corresponding t-test or that you say that you would use the p-value? $\endgroup$ – Jimmy R. Oct 18 '14 at 22:55
  • $\begingroup$ Thank you for your reply. That's the real challenge because question is asking for my own approach which is why i am not really sure which test should i choose to find out. I was also thinking for the t-test but thought maybe there is another way around to answer it. $\endgroup$ – mathsnoob Oct 18 '14 at 23:04

The scatterplot of the Miles ($X$-axis) vs Faults ($Y$-axis) indicates that

Scatterplot of Miles vs Faults 2000 and 2001

  • the number of faults has in most cases decreased in year 2001,
  • the two variables (# Faults and line length) are positively related, thus the regression coefficient is positive and probably close to $15/40=3/8$ (since in $x$ we move from $10$ to $50$ and in $y$ from $15$ to $30$).
  • the regression line does not seem to pass through the origin (though the validity of this indication should be statistically tested). In contrast, the regression line seems to cross the y-axis somewhere around $10$.

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