Exchange 'iff' with 'if and only if'

src/main/java/de/thm/arsnova/domain/QuestionBasedLearningProgress.java

@@ -22,8 +22,8 @@ import de.thm.arsnova.entities.User;
 import de.thm.arsnova.entities.transport.LearningProgressValues;
 
 /**
- * Calculates learning progress based on overall correctness of an answer. A question is answered correctly iff the
- * maximum question value possible has been achieved.
+ * Calculates learning progress based on overall correctness of an answer. A question is answered correctly if and
+ * only if the maximum question value possible has been achieved.
  */
 public class QuestionBasedLearningProgress extends VariantLearningProgress {