void write_analysis(ostream& out, const string& name,
                    double analysis(const vector<Student_info>&),
                    const vector<Student_info>& did,
                    const vector<Student_info>& didnt)
{
	out << name << ": median(did) = " << analysis(did) <<
	               ", median(didnt) = " << analysis(didnt) << endl;
}