how do you find the IQR in a ogive graph

Question

i am having trouble finding how my teacher got a number by using the IQR formula (Q3-Q1) but how do i find those quartiles in the ogive graph and how do i calculate it to get the IQR? that is basically what i need to know for the moment.

 

Answer 1

Hello, thank you for taking the time to post your question!

Like you said in your question what you need to estimate/locate on the graph is the value of Q1 and Q3. The best way to do that is to find the total number of data points (N) … that will be the highest point on the ogive graph on the y-axis. Once you have that then you can take

¼ x N to get the Q1 location

¾ x N to get the Q3 location

I hope that helps get you moving in the right direction! Feel free to reach out if you have any additional questions beyond that :)

Answer 2

Hope this helps! it helps to see how a ogive graph is constructed (from cumulative frequencies.

http://fsweb.bainbridge.edu/dbyrd/statistics/ogive.htm

 

From there you can calculate the 25% point and the 75% point to find the Q3-Q1 range.