Question About Statistical Significance


I am currently working on a project where I analyzed a company's client data and I am currently trying to figure out significances/obervations from the data. A couple of things came up when I was looking at the data that hopefully you guys/girls can help me out with.

1. If there is a plan percentage (i.e., % women) of 17% compared to overall population with 40% women, is the difference of 23% something to be concerned about or is it within range? To test significance, would I just use the t-test?

2. How do you differentiate statistical difference on percentages(%Female) versus numbers(age, tenure)?

I apologize if some of these things are rudimentary statistical concepts but it has definately been awhile since I have had to use statistics. Thank you in advance for any help.