1. How To Lie
With Graphs

2. Truncated
“Y” Axis

3. When you don’t start
the Y-axis at 0, you
overemphasize the
top part of your graph

4. This looks like a significant change!

5. Correct Version But notice that if the graph started at 0, then the
difference doesn’t
seem as significant

6. Again, this looks
like solid growth!

7. But starting at 0, it’s only a modest increase
Correct Version
But starting at 0, it’s only a modest increase

8. These next graphs all show an overemphasis on the top of the data

12. No
“Y” Axis
Labels

13. your data points really are
When you don’t label
the Y-axis, it becomes
unclear how far apart
your data points really are

14. This looks like a significant change!
Without Y-axis labels, we don’t notice the error (the vertical intervals aren’t equal).

15. Now we see that the data points *weren’t* spread apart evenly
Correct Version
Now we see that the data points *weren’t* spread apart evenly

16. Again, no way to check the spacing of the data without labels.

17. Correct Version

21. One “person” = $6.7 million?

22. Adjusting
the
intervals

23. By adjusting the intervals emphasize or de-emphasize
on the Y-axis, you can
emphasize or de-emphasize
the results of the data

24. Again, look at that growth! (and the minuscule intervals…)

25. Yet when you start at 0 (and increase the intervals) we
Correct Version
Yet when you
start at 0 (and
increase the
intervals) we
see a different
picture.

26. This seems to show a flat growth
This seems to show a flat growth. (and there’s a truncated y-axis, and there’s a graphing mistake in the last 8.6% data point)

27. Correct Version
But even if we don’t start at 0, we can decrease the intervals on the Y-axis to show a different story

28. Flipping
the “Y” Axis

29. We’re used to seeing
the Y-axis start at 0
on the bottom, and go
up from there. People
might not notice if it
is backwards, and reach
the wrong conclusion.

30. Look at those numbers go down! (oh wait, they’re going up!)

31. At first glance, this makes it seem like the number of gun deaths went down after the law was made

33. Uneven
Intervals
On Axes

34. (of course, having *wrong* intervals is just bad graphing)
If you have uneven intervals on the axes, you can skew your audience’s conclusions.
(of course, having *wrong* intervals is just bad graphing)

35. It looks like a sharp decrease, until you see that the X-axis data isn’t even

36. the decrease is more gradual
Correct Version
Spread out over time,
the decrease is more gradual

37. Axes aren’t labeled, but if they were, there are uneven intervals on the “X” Axis

38. The dates aren’t supposed to be evenly spaced apart!
Correct Version
The dates aren’t supposed to be evenly spaced apart!

39. Uneven intervals on the “X” Axis

40. Uneven intervals on the “Y” axis
(and the last data point on the “X” axis is 3 days off, making it look steeper)

41. Numbers
Not Adding Up

42. And then there’s just
bad graphs, where the
data doesn’t add up,
or an error has
been made.

43. The “whole” should be 100%

44. That’s 110% participation!

46. (Just don’t make *BAD* graphs)
So depending on the choices you make, you can often use data to persuade your audience to support your view.
(Just don’t make *BAD* graphs)