Box and whisker plot HELP (1 Viewer)

[xxheersaletixx]

hey2006 HSC General maths section 2 Question 24 cit gives you a cumalitive frequency histogram and polygon then asks for you to draw a box and whisker plot for it i have no idea how to do that :S can someone explain how to draw box whisker things from the data on a histogram?thankyou so much xo

 

[lychnobity]

So here's the thing, I can probably help you if I have the question. But I don't and I'm too lazy to go searching for it. Find it on net, printscreen, paste to paint and upload it?

 

[xxheersaletixx]

Image - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting it

 

[lychnobity]

Since it's a cumulative frequency graph, the vertical axis indicates the number of people you have (ie 60).

As normal for graphing box and whisker plots, follow these steps:
1) Find the median
2) Find the lower quartile (find the no. in the middle of the median & lowest score)
3) Find the upper quartile (" " highest " ")
4) Draw the box indicating the lower & upper quartiles, median, then the line....

In this case, look on the vertical axis to find the median. There are 60 people, so the median is between the 30th and 31st number. If you go to 30.5 on the vertical axis, then go across, the median is 155cm.

Now, the lower quartile, is found between the median and the lowest number. ie between 30 and 1. Median of these set of numbers is between 15 & 16 = 15.5 like before, go to 15.5 on the vertical axis, go across and it will be 145cm.

Repeat for the upper quartile (this one has a trick - the upper quartile is between 45th and 46th numbers. From the graph, you can see the 45th number is 165cm, and the 46th number is 175cm. Average 165 and 175 = (165 + 175)/2 = 170)

 

[PC]

To draw a box plot, you need the five number summary (Minimum, 1st Quartile, Median, 3rd Quartile and Maximum).

The question gives us the minimum (140 cm) and maximum (190 cm). We'll have to find the rest ourselves.

There are 60 people altogether (not 70, be careful). So the median is at 30 people. From the graph this looks to be at 150 cm.

1/4 of 60 is 15. At 15 people, we have a height of 145 cm.

3/4 of 60 is 45. At 45 people, we have a height of 170 cm.

So box plot with vertical lines at 140, 145, 150, 170, 190.

 

[xxheersaletixx]

=] thanks alot!

 

[lychnobity]

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