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Title screen: Building a Dot Plot. Copyright ©2017 McGraw-Hill Education. All rights reserved.
Narrator: "In this video, you'll learn how to create a dot plot. A dot plot is often considered a useful alternative to a histogram. This data set shows the wash-cycle time for 40 washing machines. We want to know how the data are dispersed along the scale, from minimum to maximum wash time. When we are finished with this data set, our dot plot will look like this one."
A dot plot, a graph with points plotted on the whole number of each y-axis increment.
Narrator: "The X-axis is the number of minutes in a washer cycle, and the Y-axis is the frequency with which a particular number of minutes occurs. This point, for example, at (35, 3), which does not have a value above it, means that three times 35 minutes occurs in the list of 40 results. Before we can build this chart, we first have to prepare our data to get the frequency count. I've already sorted my data from largest to smallest. Now I'm going to add another column called Frequency Count. I'll use a simple formula in the Frequency Count column to keep count for us."
The formula in cell B2: equals if left parenthesis A1 equals A2 comma B1 plus 1 comma 1 right parenthesis. Text: The formula says: If the value in the "minutes" cell to the left is the same as the value above it, add + 1 to the frequency count which is in the cell above this one. Otherwise, the frequency is "1".
Narrator: "The first part, A1 equals A2, that's what my IF is looking for. Does the value in A1 equal A2? If yes, use my THEN part of the formula, which says then add a 1 to my frequency count. Note that it's pointing to the cell just above this one in the Frequency Count column. And finally, if A1 does not equal A2, we get to the OTHERWISE part of the formula. "Otherwise, put a 1 here." Of course, starting at the top of my numbered list, I know that A1 doesn't contain a number, therefore we should have this 1 returned for us. With the formula set up, I can either drag it down the column or double-click the bottom right corner, and it will populate all the way down a column. Let's do that. Let's check a couple of the results. 48 occurs twice, and as you can see, the first time, it's counted as a 1, and the second time it's counted as a 2. Here's another. 42 occurs three times."
Rows 13 to 15 each contain 42 in column A. In column B, cells range from 1 to 3.
Narrator: "Now it's time to insert our graph. Select columns "A" and "B." Go to Insert, Charts, All Charts, XY Scatter, and this Frequency Count will be our dot plot."
With columns A and B selected, the button in the bottom right corner of the Chart section, found in the Insert tab, is selected. The Insert Chart dialog box appears. In the X Y (Scatter) tab of the dialog box, the first option is selected.
Narrator: "Note that it already looks a lot like the graph we showed at the beginning of the video. We could stop here, but we have come cleanup to do. Our numbers are bunched together so tightly it's hard to untangle. We don't need half-numbers on the Y-axis. This is our frequency count. We can only have frequency occur once, twice, three, four, et cetera. Right-click on your graph and choose Format Plot Area."
The Format Plot Area pane appears on the right side of the screen.
Narrator: "We'll first change the primary horizontal axis."
The drop-down arrow to the right of Plot Area Options in the pane, is clicked to select Horizontal (Value) Axis.
Narrator: "I'm going to move the graph over so that we can see it. Click on the Bar Chart icon. Under Axis Options, change minor units to 1. Change the bounds to a minimum of 25. We don't have any values very far below that. And you can see already that the dots spread out."
The Bar Chart icon is selected at the top of the pane. With Axis Options expanded, Minimum is set to 25, Maximum is set to 50.
Narrator: "Now we move to the primary vertical axis. And on the primary vertical axis, let's change the minor units to a 1, and the major units to a 1. Our maximum value is a 4, so we can go ahead and change that, as well."
Axis Options at the top of the pane is changed from Horizontal (Value) Axis to Vertical (Value) Axis. Under Units, Major and Minor are set to 1. Under Bounds, Maximum is set to 4.
Narrator: "Now we can close this sidebar in order to have some space. I'm moving the graph to the left so that we can see all of the options. Click the checkmark, go to Gridlines, and where it says Minor Vertical, when we click it, you can see that it fills in faint lines on the graph that make it easier for us to see where dots are placed."
The plus button outside the top right corner of the chart is selected to reveal the Chart Elements list of checkboxes. Gridlines is expanded to check Primary Minor Vertical.
Narrator: "We're almost done. Now we just need to change Frequency Count to the title that we want to have here. That's more descriptive. We'll change that to Washer Minutes."
The chart title is edited by clicking its default text.
Narrator: "And we are done. In this video, we have walked through how to use the IF function to create a frequency count of the values in a set of data, and then, using the XY Scatter chart, build a dot plot."
Video has ended.
Described transcript ©2023 McGraw Hill. All rights reserved. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.
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