Constructing a time series plot

Intro

Howdy! I'm Professor Curtis of Aspire Mountain Academy here with more statistics homework help. Today we're going to learn how to construct a time series plot. Here's our problem statement: The company data represent the percentage of recent high school graduates graduated within 12 months before the given year end who enrolled in college in the fall. Construct a time series plot and comment on any trends.

Part 1

OK, to construct the plot, we need actual data.  So we're going to click on this link here, and here's our data.  Now we're going to put that data into StatCrunch.  OK, we've got the dated loaded here in StatCrunch.  I'm going to resize this window so we can see everything a lot better.

And now making the graph in StatCrunch is pretty easy.  I just go up to Graph --> Index Time Plot.  In the first area, I'm asked to select the columns that I want to graph, and this is what's represented on the y axis.  So you can see here with our answer choices, the percent enrolled is on the y axis. So I'm going to select that there.

Then down below, see how there's a format for the x and y axis, and you've got different options that you can go with?  We actually want Time because our data is separated into years, so we're going to select Years under Type.  And the starting year — the first year of our data is 1989, so I'll put that in.  And then each data point proceeds increments of every one year.  So we're just going to leave that default value there.

And that's all we need to do. I press Compute!, and here is my time series graph.  Now I just look for the answer option that best represents what I have here in StatCrunch, and clearly that's going to be answer option A.  Excellent!

Part 2

Now the second part of the problem asks us to comment on any trends.  There's three answers that we have to choose from, so let's see what we're looking at here.  Generally, if you look at the graph here, the trend starts out low, comes up high, and there's a down spot here and then it comes back up high again.  So if you look at all of the data points and try to imagine a line of best fit going through all of the data, that line would be going upward as we go from left to right.  So the general trend, even though there's some lows is increasing from left to right or increasing with time because from left to right we're increasing with time.  So let's see which answer option best matches that.  It looks like answer option A.  Well done!

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