# C3\_W4\_Assignment - Exercise 3

**URL:** <https://community.deeplearning.ai/t/c3-w4-assignment-exercise-3/467004>\
**Category:** Probability & Statistics for Machine Learning &...\
**Tags:** week-module-3\
**Created:** [October 10, 2023, 4:21pm UTC](https://community.deeplearning.ai/t/c3-w4-assignment-exercise-3/467004 "2023-10-10T16:21:10Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![LukeNukem](https://avatars.discourse-cdn.com/v4/letter/l/f0a364/32.png) [@LukeNukem](https://community.deeplearning.ai/u/LukeNukem)\
**Post date:** [October 10, 2023, 4:21pm UTC](https://community.deeplearning.ai/t/c3-w4-assignment-exercise-3/467004/1 "2023-10-10T16:21:10Z")

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Hi there,

I’m a bit stuck on this exercise as I don’t understand how I should calculate mu1 - mu2 for the t statistics.

As I understand it, we only have a sample (not the population) of users who visit my website. These users are divided into two groups. So I can calculate xbar1 and xbar2.

But I don’t understand what mu1 and mu2 should be in this context.

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<div class="post-metadata">

**Author:** ![TMosh](https://sea1.discourse-cdn.com/dlai/user_avatar/community.deeplearning.ai/tmosh/32/9321_2.png) [@TMosh](https://community.deeplearning.ai/u/TMosh)\
**Post date:** [October 10, 2023, 6:52pm UTC](https://community.deeplearning.ai/t/c3-w4-assignment-exercise-3/467004/2 "2023-10-10T18:52:31Z")

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Indirectly, the x-bar and s values are computed using the compute\_continuous\_metrics() function.

And that in turn should implement the methods for the estimation\_metrics\_cont() class.

It all ties together via these instructions:

 ![image](https://global.discourse-cdn.com/dlai/original/3X/8/0/8004d5fefd441b8b1823fd4c19e8dad76f43ba7f.png)

It’s a bit complicated, and I’m not sure whether that’s a good thing.

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<div class="post-metadata">

**Author:** ![TMosh](https://sea1.discourse-cdn.com/dlai/user_avatar/community.deeplearning.ai/tmosh/32/9321_2.png) [@TMosh](https://community.deeplearning.ai/u/TMosh)\
**Post date:** [October 10, 2023, 7:00pm UTC](https://community.deeplearning.ai/t/c3-w4-assignment-exercise-3/467004/3 "2023-10-10T19:00:44Z")

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For mu1 and mu2, note this instruction:

 ![image](https://global.discourse-cdn.com/dlai/original/3X/8/5/852d88fb9a49d0d8fbe62418b92cac0ace599cc4.png)

Under the null hypothesis, this is 0-0 = 0. (i.e. the null hypothesis assumes there is no significant difference between the populations).