Chi-Square vs t-test


I am trying to compare observed education levels of a visiting group to the expected (known) education levels of the nation.

These are my figures:

Observed: 71% (have degree) 29% (no degree)
Expected: 27% (have degree) 73% (no degree)

If I use chi-square how can I determine the strength (crater's v?) without more info other than the number (which I do have)?