Determining if checkbox is checked in Ionic 2

How can I determine if a ion-checkbox is checked in Ionic 2.

   <ion-item *ngFor="let a of q.Answers">
      <ion-label></ion-label>
      <ion-checkbox (click)="addValue($event)" [(ngModel)]="a.checked"></ion-checkbox>
   </ion-item>

the following return undefined

 addValue(e): void {
     var isChecked = e.currentTarget.checked;
     console.log(isChecked);//undefined

 }