Setting up quality control

Quality control lets you get more accurate responses and restrict access to tasks for cheating performers. Quality control consists of rules. All rules work independently.

Attention.

Quality control settings in a customizable project are applied to all project pools, so you can't change them in just one of the pools.

When you clone a project, its quality control settings aren't transferred.

To set up quality control:
  1. Open the project page.
  2. Go to the Quality control tab.
  3. Click Set quality control.
  4. Click Add Quality Control Rule.
  5. In the list that appears, select the appropriate rules. If you aren't sure what quality control rules you need, select a ready-made protection set of rules with default settings.
  6. Make settings for the rules you added. Below is a list of rules with links to detailed information about the rule settings.

List of rules

Troubleshooting

How do I set quality control in a pool correctly?

The settings for quality control rules depend on the type of tasks. General recommendations:

  • Always use one or more ways to control quality of answers.

  • Counting fast responses makes sense for most tasks.

  • If the user has to choose between options (for example, by selecting checkboxes), check the answers using majority vote or control tasks.

  • If the user has to provide a response as a text or link or upload a photo, the best way to control quality is by reviewing assignments. You can outsource task acceptance to performers. Create a task with a question (for example, “Is this phrase translated correctly?”) and possible responses (for example, “yes”/“no”). Set up overlap and majority vote check.

  • If a task is more like an opinion poll (for example, choosing nice pictures from a set), majority vote is not a good way to control quality. Make control tasks with artificial examples where the choice is evident.

How many control tasks do I need to add?

We recommend adding at least 1% of control tasks in the pool. And for small pools — 5-10%.

Why's that?

Each control task is shown to the performer only once. If you use smart mixing, you determine how many control tasks should be in a suite. If each suite contains one control task, then the maximum number of suites the performer can complete is equal to the number of control tasks in the pool. If you increase the number of control tasks in a suite, the number of suites available to the user decreases by the same number.

There shouldn't be too few pages available. Otherwise:

  • You won't be able to correctly evaluate the quality of the performer's responses.
  • The performer won't be interested in completing such tasks because they'll spend a lot of time studying instructions but won't earn much.
Example
A large pool with 1% of control tasks (good)

There are 10,000 tasks in the pool, and 100 of them are control tasks (1%). Each suite contains 10 tasks, and 1 of them is a control task. Hence, a user can complete up to 100 suites.

A small pool with 1% control tasks (bad)

There are 100 tasks in the pool, and 1 of them is a control task (1%). Each suite contains 10 tasks, and 1 of them is a control task. Hence, each user can only complete 1 suite.

A small pool with 10% control tasks (good)

There are 100 tasks in the pool, and 10 of them are control tasks (10%). Each suite contains 10 tasks, and 1 of them is a control task. Hence, each user can complete up to 100 suites

If there are few control tasks in the open pool, add new control tasks.

What for

In a large pool with few control tasks, a situation might occur when users who have completed a lot of tasks in the project stop getting new task suites. This happens when the user completes all control tasks in the pool.

Note.

To filter out performers, use the Control tasks quality control rule. To rank performers by the quality of responses in control tasks, use a skill.

How are the correct responses to control questions counted?

The Control tasks rule starts working after the performer completes the number of control tasks you specified. If your pool contains both training and control tasks, you can take into account the responses in both of them (the Number of responses parameter) or only in control tasks (the Number of control responses parameter).

As soon as the needed number of responses is collected, Toloka calculates the percentage of correct and incorrect responses and performs an action (assigns a skill, or blocks the user in the pool or in the project). Then this percentage is updated as the tasks are completed by the performer. The number of the performer's recent responses that's used in the calculation is set in the Recent control task responses to use field. If you leave it empty, all the responses from the performer in the pool are counted.

Should I create a skill for every pool?

It is better to use one skill in a project. You can choose the way to calculate the skill:

  • Calculate the skill for each pool separately. The current skill value is the value of the skill in the pool the user completed last. This option is convenient if:

    • The pools are intended for different groups of performers (for example, there are filters by city or country).

    • Pools are started one by one and you don't want to take into account the responses in the previous pools to calculate the skill in the current pool.

    This calculation method is used by default when adding a quality control rule to a pool. For the control tasks block, leave the Recent control task responses to use field empty.

  • Calculate skill based on all tasks in a project This option is good if the pools are small and you don't need to have skill calculated for each pool.

    This option is available only for skills on control tasks. To use it, fill in the Recent control task responses to use field in pool quality control rules.

Can I use a skill beyond a particular pool or project and apply it to other projects as well?

Yes, of course — you can use the same skill for different projects. But most often, a skill is intended for a specific project. If the performer completes a certain task well, this doesn't mean that they will complete other ones successfully. Another disadvantage is that if you filter by skills that were set long ago, you will artificially limit the number of available performers.

Can I disable tasks for performers who do a poor job on tasks?

You can deny access to the pool if the performer's responses are too fast, if they don't match the majority vote, or if the performer makes too many mistakes in control tasks. Tasks completed by such performers can be given to other performers.