A Friend's Help
Storyboard Text
- Hey Ellie! How are you?
- Oh why? What's the problem?
- Hi Chris! I'm doing alright. Just a bit worried though.
- Well then come on, we'll take a walk while I teach you
- Hmm, you mean the lesson about test statistic? About determining the right one to use?
- Well, exam week is near and I still haven't understood Miss Belle's last lesson
- Yeah, that one!
- So, just as a recap, we will be mentioning population standard deviation and sample standard deviation. Varian and mean will also be mention but not as much as the other two. We also have two tests: z-test and t-test. Have you already understood these?
- Yeah I already understood those. I learn all their formulas yesterday. I also know how to determine them in a given problem. Those were the easy parts.
- Well, then think of it this way. Imagine there is a crosswalk leading to 2 ways. One is for when your sample is greater than or equal to 30 and the other is when it is less than 30. When you go to the left road, you will reach z-test town.
- Well what if you go to the other road? If I have less than 30 samples?
- --- GREATER THAN 30OR LESS THAN 30 ---
- Then you will be facing another crossroad. This time it is when you know the population standard deviation or not. If you do know, you will still be going to z-test town. If not the you will be going to t-test town.
- So does that mean I'll only use the t-test when my sample is less than 30 and if I don't know the population standard deviation?
- --- PSD IS KNOWNORPSD IS NOT KNOWN ---
- Yeah that's it basically.
- No problem Ellie! Goodluck on your exams.
- OMG! Thank you so much Chris! I think I might get a perfect score because of your help.
- Alright, let's go!
- Come on! Let's drink some coffee, my treat. As a way of thanking you for you help.
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