On Taskhelper, a member's track record may be determined by looking at their star ratings, reviews, and completion rates.

Star rating and reviews: A member's star rating, which is a number out of 5, is determined by averaging the reviews and stars they have accrued over their career.  

Task completion rate: the task completion rate displays the percentage of tasks that a Helper has completed out of all those that they were assigned. A good completion rate is a measure of the reliability of a Helper.
Only cancellations brought on by the Helper will have an influence on their rate. The completion rate is only displayed if the user has been assigned access to 5 or more Tasks.

Before choosing a Helper for your task, have a look at their star rating, completion rate, and reviews. You may therefore post tasks and work on them knowing what to expect.