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- no ma'am.
- okay class, that's it for today! you guys have any extra question?
- no ma'am.
- come and follow me, the rest of you can go home now.
- ahm.. to be honest ma'am. i was quite confused with how the variance was known.
- okay class, that's it for today! you guys have any extra question?
- goodbye and thank you ma'am.
- so, how can i help you?
- on how to determine the appropriate tool when the variance is known, i'm really sorry ma'am that i didn't catch up with the lesson earlier.
- it's okay, it is quite easy tho. the tool that you can use to find if the variance is known, is z-test and to find if it is unknown, you will use t-test.
- thanks ma'am, but how do i know it's difference?
- t-test reeferes to univariate hypothesis based on t-statistic, wherein the mean is known, and population variance is appproximated from the sample.
- on the other hand, z-test is also a univariate test that is based on standard normal distribution.
- one more quetion ma'am. so, in central limit theorem, i can use z-test but i have to replace the population standard deviation by sample in the formula?
- yes, you're right!
- cool, thanks for clearing this up ma'am. i totally understand it now.
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