Reading bar charts: comparing two sets of data | Pre-Algebra | Khan Academy

A bar chart is especially useful with comparing two sets of data. The difference in the bars give us a quick snapshot that allows us to draw some conclusions.

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Closed Caption:


So we have this bar chart here.
This says Scores on
Midterm and Final Exams.
So this axis, the vertical
axis, is the scores.
And then it's by student.
And the blue bar is the
midterm, and the yellow bar
is the final.
And the question they ask
us is by how many points did
Nadia's score improve from the
mid-term to the final exam?
So let's look at Nadia.
So this is who we're
talking about-- Nadia.
And we care about how
many points did she
improve from the
midterm to the final.
Midterm is blue,
final is yellow.
So on the midterm, it
looks like she scored--
and if I were to eyeball
it, it looks like 75 points.
And on the final, it
looks like she scored 80.
It looks like she
scored 85 points.
So it looks like her score
improved by 10 points,
so 10 points.
Let's try one more.
How many students improved
their scores from the midterm
to the final exam?
So to improve from the
midterm to the final, that
means that the yellow
bar for a given student,
which is the final, is going to
be higher than the midterm bar.
That's the only way you can
improve from the midterm
to the final.
So Brandon improved from
the midterm to the final.
Vanessa improved from
the midterm to the final.
Daniel improved from the
midterm to the final.
Kevin improved from the
midterm to the final.
William got a lower score on
the final than the midterm,
so he did not improve.
So the number of students
that improved their scores
from midterm to final are
one, two, three four students,
so 4 students.