I'm writing an article on pyelonephritis in children and for this I've come across a statistical problem, seeing as my statistical skills are very limited.
My data is devided into three groups: group A: children younger than 6 months, Group B: Children between 6 months and 3 years, group C: children older than 3 years.
For these three groups I've found frequences of abnormal lab findings, abnormal ultrasound etc.
In order to compare these three groups statistically - as in: is the frequencies of abnormal lab findings or abnormal ultrasound significantly different? - I've been told I need to use af Chi square test with two degrees of freedom.
Can anybody tell me where I can find a calculater for this or help me in any other way.
thanks in advance for any help