Testable hypotheses construction; minimum predictive strength vs. significance
Good question.  By convention, the null hypothesis is always framed to say there is no statistical relationship between one or more independent variables and a dependent variable.  This is typically tested at the p &lt; 0.05 level.  The level of the relationship beyond it being significant is not addressed in a null hypotheses.  (See, for example, Encyclopedia of Research Design, edited by N.J. Salkind, 2010).  As for testing the "70% confidence" result, there is no way to do that.  That is the statistical result.  The overall validity of a logistic regression model can be assessed using Pearson's chi-squared, R-square, and classification accuracy.