Finding the coefficient of variation for parking meters

Intro

Howdy!  I'm Professor Curtis of Aspire Mountain Academy here with more statistics homework help.  Today we're going to learn how to find the coefficient of variation for parking meters.  Here's our problem statement: Listed below are amounts in millions of dollars --- millions of dollars, I like the sound of that! --- collected from parking meters by a security service company and other companies during similar time periods.  Do the limited data listed here show evidence of stealing by the security service company's employees?

Part 1

OK, the first part of the problem asks us for the coefficient of variation for the amount collected by the security service company.  Of course, the next part's going to ask for all the other companies, so let's go ahead and dump our data into StatCrunch.  I can resize this window so we can get a better look at everything.  Excellent.

Now I'm going to go into Stat --> Summary Stats --> Columns.  I know I'm going to have to do both my columns, so let's just go ahead and just select both of them.  And notice how I selected both of them, by holding down the Ctrl button on my mouse while I clicked the other option that I wanted.  And then the statistic I want is the coefficient of variation.  So I select that, hit Compute!, and boom!  Here's my coefficients of variation.

Notice that coefficients of variation are listed as percentages.  So there's no need to adjust your decimal point to, you know, uh, you know, change the number out to its proper form.  It already is in the proper form.  It's asking for a percent here.  So we're asked to round to one decimal place, so I'm going to do that.  Good job!

Part 2

Now the second part asks for the coefficient of variation for the amount collected by the other companies.  Of course, we've already calculated it, as you can see here.  Again, one decimal place, so I need to round my number to [that].  Well done!

Part 3

Now the last part of this problem asks, "Do the limited data listed here show evidence of stealing by the security service company's employees?  Consider a difference of greater than 1% to be significant."  Well, what's the difference between our coefficients of variation here?  It's about 3% three percentage points.  So that's definitely greater than one percentage point.  So yes, there is a significant difference in the variation.  Excellent!

And that's how we do it at Aspire Mountain Academy.  Be sure to leave your comments below and let us know how good a job we did or how we can improve.  And if your stats teacher is boring or just as I want to help you learn stats, go to aspiremountainacademy.com, where you can learn more about accessing our lecture videos  or provide feedback on what you'd like to see.  Thanks for watching!  We'll see you in the next video.