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## AP®︎/College Statistics

### Course: AP®︎/College Statistics > Unit 1

Lesson 2: Representing a categorical variable with graphs# Reading bar charts: comparing two sets of data

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. Created by Sal Khan.

## Want to join the conversation?

- At0:38Sal said 80 and 85. what is the answer?(3 votes)
- 85. He's not really saying 80, he's just hesitating a bit the first time and starts over saying 85. Looks like 80... like 85.(20 votes)

- when ever the blue line is not all the way on a number will it allways be 5?(4 votes)
- On the Khan Academy practice shown, yes, because they're counting by tens on the y-axis scale and the bars in between are always exactly half way in between.

In other situations, though, not always. You have to look carefully at the bar and the y-axis scale to see where the bar is and what they're counting by.(4 votes)

- Why do I get more energy points from watching a video than from answering 7 questions right?(2 votes)
- what if the bar is in between the line(2 votes)
- If the bar ends between two lines you just estimate where it ends. In the example on the video they all end halfway between the two numbers, making it 5 points more than lower of the two numbers.(1 vote)

- At0:32it says about 75 points. I tried to guess the amount of points in Reading bar charts 2 and I said I said it looked like 42 but it said I was wrong. How am I supposed to know the exact amount?(1 vote)
- This seem like a practice video ,where can I learn statistics from the basic level to the most advance level on this website(1 vote)
- why does there have to be 6 things why can't it just be less than 6(1 vote)
- Wy do all of Sal's videos sound like they are outside.(1 vote)
- why does Sal always say things twice(0 votes)
- he is pretty old like 50 his mind isn't perfect deal with it.(3 votes)

- why do people always use these and how is it that the sun light and the speed of sound combined to form a single equation can work?(1 vote)

## Video transcript

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.