Toloka documentation

Quality control rules

Quality control rules allow you to get more accurate responses and restrict access to tasks to cheating Tolokers. All rules work independently.

List of rules

Quality control presets

Toloka has presets of quality control rules. Currently, there are three of them:

  • Elementary — suitable for requesters who need tasks to be completed by a large number of Tolokers in a short time.

  • Basic — suitable for those who need to balance quality and quantity.

  • Advanced — a set with a large number of rules required for complex tasks.

The table shows the rules included in each of the sets.

Earnings Skipped assignments Control tasks Majority vote Submitted answers Fast responses
Elementary + + -
Basic + + + + -
Advanced + + + + + +

How to set up quality control

You can configure quality control in the pool and in the project.

Go to pool editing (click in the upper-right corner of the page) and click Add Quality Control Rule in the Quality control section.

You can copy quality control settings from another pool. To do this, click Copy audience filters and quality control settings in the Audience section.

Open the project page, open the Quality control tab and click Set quality control. Then click + Add Quality Control Rule.

The rules are applied to all project pools, so you can't change settings in just one of the pools.

Restriction

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

See also

For developers

Troubleshooting

Setting up quality control
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 Toloker has to choose between options (for example, by selecting checkboxes), check the answers using majority vote or control tasks.

  • If the Toloker 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 Tolokers. 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.

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 Toloker completed last. This option is convenient if:

    • The pools are intended for different groups of Tolokers (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 Toloker 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 Tolokers.

I set up quality control, then I copied my user requirements. All my quality control settings were deleted and replaced with the copied settings. Is that normal?

Yes. When you copy the filter and quality control settings, the settings you previously added manually are overwritten. You should see a warning about this in the copy settings window.

Is the time specified per task suite in the fast response settings?

Yes, the fast response settings specify the time per task suite.

Have I understood correctly that if I use set the the skill value = 1 with the percentage of accepted responses >= 75 and 10 recent values to use, for every 8 correctly completed tasks out of 10 the Toloker is given 1 skill point?

No, this is incorrect. With these settings, each time a rule condition is met, the Toloker gets skill = 1. To change the skill value in the process of task review, you need a “multi-step” rule, which has multiple identical rules with different values of Total reviewed responses.

Overlap
What overlap should I set?

Overlap defines how many Tolokers complete the same pool task.

The best overlap is an overlap that provides satisfying quality of results. For most tasks that are not reviewed, overlap from “3” to “5” is enough. If the tasks are simple, overlap of “3” is likely to be enough. For tasks that are reviewed, set overlap to “1”.

Can I change overlap after the pool is started?

Yes. Open edit mode for the pool and set a new overlap value. You don't need to restart the pool. Updating the settings is usually fast, but if there are many tasks, it may take several minutes.

Banning Tolokers
The pool has an overlap and majority vote set up, but some fraudulent user opens the task suites, does nothing, and submits empty assignments. Could this cheater get more tasks from the pool before the results of other Tolokers are known? Could a user quickly click through a lot of task suites before the majority vote is accumulated to ban the cheater?

Yes, unfortunately, this can happen. This is why we recommend that you offer a training task or exam before the general task. In this case, only those people who showed good performance at the previous stage are selected for the main pool.

If a cheating Toloker gives a lot of incorrect responses, and the system eventually bans them for errors in control tasks, do I have to pay for the bad responses anyway?

If the Toloker already got paid for the tasks, the money can't be refunded to you.

Can one Toloker get access to two pools in the same project? Can I avoid that?

Yes, if they can access both pools, they can do both of them. To restrict access to subsequent tasks for a Toloker, use the Completed tasks rule and select a ban at the project level.

If I ban a Toloker for doing my tasks too fast, will all their responses be deleted and given to other Tolokers for labeling?

No. The responses of these Tolokers aren't automatically excluded from the final results file.

But you can do it yourself if you want. When downloading the results, select the option Exclude assignments by banned users to delete the responses of Tolokers who were banned at the moment of downloading. You can also forward all the assignments from banned users to other Tolokers using the Re-completion of assignments from banned users rule.

If I ban users from my project so that everyone can complete a maximum of one task, are the Tolokers notified of the ban?

No, the Tolokers are unaware of the ban.

Majority vote
What output format do I use for the review results to filter out mismatching users based on the “Majority vote”?

To perform actions with users (assign a skill or ban them) based on the majority vote, add a relevant rule to the pool.

Don't forget to enable Keep task order in the pool parameters. Majority vote is used in the projects with preset options (radio buttons or checkboxes). This rule won't apply to the text entry or file upload fields.

My task uses a form with multiple fields. When there is an overlap and “Majority vote” is used for quality control, is each field taken into account, or if one field mismatches the majority vote, are the task results considered incorrect?

All responses to the task are taken into account. If one response differs from the majority vote, the whole task is counted as mismatching the responses of other Tolokers.

Control tasks
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 Toloker 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 Toloker 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 Toloker 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 Toloker's responses.
  • The Toloker 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 Toloker completes all control tasks in the pool.

Note

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

If I upload tasks using smart mixing, does it mean that the same file should contain both the control tasks and general tasks, or can I upload them separately?

Smart mixing is set up when you upload tasks to the pool. After creating a pool, click Upload and select the method for generating task suites. You can upload them using separate files or one file, arranging them in any order.

How are the correct responses to control questions counted?

The Control tasks rule starts working after the Toloker 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 Toloker in the pool or in the project). Then this percentage is updated as the tasks are completed by the Toloker. The number of the Toloker'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 Toloker in the pool are counted.

I created a training pool with one task containing a hint. The Toloker fails to complete the task on the first attempt, but finally succeeds. The Toloker gets the skill 0. How do I grant to the Toloker access to my tasks? The minimum required level that you can set is 10.

Technically, if you have only one task in your training pool, you don't have this option. The skill will be either 0 or 100. We recommend that you add several tasks, or at least 2 so that the Toloker will practice on the first task and will be able to do the second task correctly. In this case, you can admit users to your main pool starting from the skill value of 50.

You can also create a training pool based on the main pool. Assign a skill using the Control tasks rule: in this case, you can admit users with any skill level to your main pool, even if the value is zero. But we don't advise giving tasks to people who failed training.

Can the Tolokers see which questions are control tasks?

No, they can't.

When I export a project from the Sandbox, the task files are not exported. Is this how it's supposed to work? I suddenly lost the markup of the control tasks that I created in the sandbox.

The tasks themselves are not exported, only the project configuration and the settings of the selected pool. However, you can download your marked up tasks from the Sandbox pool and import them to the pool you created. To download the control tasks only (if you marked them up in the interface), go to Mark up, then click Control tasks and Download.

In the section about control questions, does "Number of control responses" mean the total number of responses to control questions (including incorrect responses) or the number of correct responses to my control questions?

This is the total number of responses to the control questions.

How do I classify users as good Tolokers and poor Tolokers as they complete tasks, and ban the poor Tolokers?

You can create a task pool for all your Tolokers and create Toloker skills in it. In this case, you can open your tasks only to the Tolokers with the necessary skills.

Can I make my training or control tasks totally different from the general tasks?

Your training and control tasks have the same project specification. However, you can create a separate project with the tasks and assign a skill based on user responses. Then you can admit Tolokers to the main project based on their skill.

Isn't the exam a regular pool that I pay for? How does it differ from a regular pool?

An exam pool contains only control tasks. It's usually small and used for checking how well users learned to do your tasks after they read the instructions and completed the training. Unlike your main pool, you already know the correct responses for every task in this pool. You can set the price to zero.

Based on the results of responses to control tasks, you can assign a skill to the Tolokers and then specify it in the main pool as a filter. For example, MySkill = 80 or = Is missing. You don't have to create an exam. For simple tasks, the training pool provides enough practice, but many requesters also use exams.

How do I set up an exam so that different people can take it without running out of tasks?

When you load tasks, use smart mixing. In this case, you'll have infinite overlap in your exam.

However, this poses the risk that you might spend a lot of money on the exam. You might want to open this pool only when the main pool opens, and close it when labeling of the main pool ends.

How do I test users to determine which kinds of tasks they do better and assign them relevant tasks?

You can add a training pool to test your Tolokers. Based on the test results, assign skills to the Tolokers for the tasks they do best.

Then open your pools only to the Tolokers that have a certain skill: use filters for this.

Can I create two active training pools, one for practice and the other for admitting users to the main pool? In other words, one pool is for users to practice and the other pool tests them.

Yes, you can do that. In this case, create the first pool based on the training pool and the exam pool based on your main pool. If a pool contains only control and/or training tasks, the price can be set to zero.

In the exam pool, you can create a skill reflecting the exam result and granting admission to the main pool. For example, if the number of responses is ≥ 10, set the skill value in the <exam skill> as % of correct responses. In your exam pool user requirements, specify: <exam skill> < 80 or = Is missing>. In the main pool, set up a filter: <exam skill> >= 80 and (<main skill> >= 70 or = Is missing). You can choose the skill values depending on how well the Tolokers handle your task.

I want to create an exam with three tasks. If a user does two out of three tasks correctly, they get the skill. So I try to use 3 in the Recent control task responses to use field, but I get an error that the value is too small. Can I get around this without increasing the number of tasks to five?

The Recent control task responses to use field is for the number of recent responses from the Toloker. If you use manual review for your task, then to set up your intended rule you need to specify 3 in Total reviewed responses.

Speed of task completion
Why has the speed of pool completion dropped?

Possible reasons:

  • You've stopped the main pool. This could limit the number of Tolokers with access to the pool. Start the training pool again. There will be more Tolokers who can access the tasks.

  • The filters you set are too strict. For example, a strong restriction on a certain skill that most users don't have.

  • Too many users are banned. Ease the quality control rules.

How can I speed up the pool completion?