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# Help with S1 - Normal Distribution Watch

1. We just started Normal Distribution in S1...and the things are going completely over my head. Guys, help!

Firstly, the examples in my book all use graphs to solve the sums. Which I don't get AT ALL. Our teacher didn't use graphs...he kind of explained it as "Check the left hand side. If it shows greater than, you subtract it from one. Then check the right hand side". Then there's something with being "greater than 0.5" and something with minuses. I don't get it at all.

Could someone just explain the whole thing from the top to me?

Okay here's two sums:

1. The random variable Y~ N (µ, 40) and P (Y< 25) = 0.15. Find the value of µ.

2. The random variable Y ~ N(50, σ²) and P(Y>40) = 0.6554. Find the value of σ.
2. (Original post by You-know-who)
We just started Normal Distribution in S1...and the things are going completely over my head. Guys, help!

Firstly, the examples in my book all use graphs to solve the sums. Which I don't get AT ALL. Our teacher didn't use graphs...he kind of explained it as "Check the left hand side. If it shows greater than, you subtract it from one. Then check the right hand side". Then there's something with being "greater than 0.5" and something with minuses. I don't get it at all.

Could someone just explain the whole thing from the top to me?

Okay here's two sums:

1. The random variable Y~ N (µ, 40) and P (Y< 25) = 0.15. Find the value of µ.

2. The random variable Y ~ N(50, σ²) and P(Y>40) = 0.6554. Find the value of σ.
http://www.examsolutions.net/maths-r.../S1/module.php

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