First Time Statistics Problem

This is the last problem for an assignment I am working on and I've tried to come at it several ways but keep coming up blank. Here it is:

The city's Department of Transportation has been keeping track of accidents on a particularly dangerous stretch of highway. Early in the year, the city lowered the speed limit on this highway and increased police patrols. Data on number of accidents before and after the changes are presented below. Did the changes work? Is the highway safer Construct a line chart to display these two sets of data (use graphics software if available)

Month 12 Months Before 12 Months After
Jan 23 25
Feb 25 21
Mar 20 18
Apr 19 12
May 15 9
Jun 17 24
Jul 24 11
Aug 28 15
Sept 23 17
Oct 20 14
Nov 21 18
Dec 22 20

All my book tells me is to use midpoints. I'm not sure how to construct my graph other than there will be two lines (one for before and one for after). Thanks for the help in advance


New Member
Just make two timelines with the values that you have in the data.

I made an example in excel for you so you can see how it could be done. I used made up data with number of products sold the week before and after an advertising campain.