Is Goblins free for teachers?

Yes. Goblins offers a generous free tier that includes 1 live feedback assignment per week, insights on student mastery and replays, and the ability to upload your own content. The Max plan adds unlimited assignments, superadaptive mode, grade exports, standards growth reports, and SSO/LMS integration, with per-student pricing for schools and districts.

How does Goblins work?

Three simple steps: (1) Share an assignment from thousands of standards-aligned topics using a share code. (2) Students speak and draw their thinking naturally, and Goblins responds with Socratic questioning that sounds just like their teacher. (3) Teachers get real-time formative insights showing what students struggle with and suggestions to inform instruction.

Does Goblins prevent cheating?

Yes. Goblins uses a purpose-trained AI model that evaluates cheating signals in real time. It can detect when students are copying answers, using external tools inappropriately, or not genuinely working through problems. Copy-pasting answers is also blocked.

Can I use my own voice with Goblins?

Yes. Teachers can record their voice and take a selfie to create a custom 3D avatar in about 30 seconds. Students then hear help in their own teacher's voice and see a familiar face, making the experience more personal and effective.

What math levels does Goblins cover?

Goblins covers math from Grade 5 through AP Calculus, including thousands of standards-aligned topics. Teachers can also upload their own content for custom assignments at any level.

Is Goblins FERPA compliant?

Yes. Goblins is FERPA and state compliant. Student data privacy and security are a top priority.

Does Goblins support English Language Learners?

Yes. Goblins supports 30+ languages so teachers don't have to translate every worksheet. It is especially helpful for ELL students who need accessible math instruction in their native language.

MM.19.c

Use the central limit theorem to construct a normal sampling distribution for the sample mean when conditions are met.

Example Problems

A tutor reviewed composite scores from a random sample of 14 practice tests taken by students preparing for a standardized exam. The sample was roughly symmetric with a mean of 640 points and a standard deviation of 52 points.

Based on this sample, write the expression for a 99% confidence interval for the mean composite score (in points) on these practice tests.

A nutrition researcher measured the sugar content of energy bars by sampling 9 bars from a large batch. The sample distribution was roughly symmetric with a mean of

22.1 \text{ g}

and a standard deviation of

3.9 \text{ g}

.

Based on this sample, what is the 95% confidence interval for the mean sugar content (in g) per bar?
Round your answers to the nearest hundredth.

A safety engineer measured the noise level from a production machine by taking a random sample of 6 readings during steady operation. The sample data were roughly symmetric with a mean of

62.3 \text{ dB}

and a standard deviation of

1.8 \text{ dB}

.

Based on this sample, write the expression for a 99% confidence interval for the mean noise level (in dB) for this machine.

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