Question

help!!

Answer 1

@pitamar

Answer 2

Ok, do you know to read this kind of plots? (Box and whisker plot)

Answer 3

nah I don't.

Answer 4

ok, it's actually not very hard. The whole point in those plots is to divide the 'data' into 4 equal-size groups.
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Answer 5

sorry about the drawing.. anyway. as you can see there are 4 sections here. 2 inside boxes, and 2 between those lines.
The groups vary in their length as you can see, but there will always be 4 groups.

Answer 6

In your case, each group describes a quarter of the students.
A longer group means that this quarter of the students got more varying scores.
A shorter group doesn't mean less students, it still represents a quarter of the students, but it means their scores are closer to each other.

Answer 7

for example, let's look at the left box for Class A plot. We see it starts at 65 and ends at 75.
We know now that 1/4 of the students in class A got between 65 to 75
Clear so far?

Answer 8

Clear.

Answer 9

The median is the value that half of the data is above and half below. In our case, the score that half the students got above and half got below.
Since every box or whisker is a quarter, it means that the left box and whisker represents half of the students and so does the right box and whisker.
So that means that the middle line (between the boxes) is the median, the score that half got above and half below.

Answer 10

a is not true correct?

Answer 11

correct, because you can see that the median is equal for both classes (75)

Answer 12

what is the lower quartile?

Answer 13

well, it's the median between the lowest data... and the median.
Means, if we take our median, and take the half that got below that score, now we can take a new median in here.
The lower quartile is basically the left edge of the left box.

Answer 14

Is that clear? or confusing?

Answer 15

okay.

Answer 16

so b is not true? correct?

Answer 17

@pitamar

Answer 18

Sorry, the site stopped working for me =(
As for the problem:
The lower quartile would be the score which exactly quarter of the students in the class got less than.
We can see from the plot what is that score for Class A and what is it for Class B, then we can tell which is bigger =)