Tham KY's answer to QN's Junior College 1 H1 Maths Singapore question.
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pls verify...
Date Posted:
4 years ago
I’m using old GC,
Why do I invNorm(0.95,0,1) instead of invNorm(0.05,0,1)?
Why do I invNorm(0.95,0,1) instead of invNorm(0.05,0,1)?
Old GC can only do "less than", ie only for P(Z<...)=..., or P(X<...)=...
The probability of 0.05 refers to the Right side, ie "more than"
Since the claim is accepted, does the z-test lie within or outside the critical region?
H1 is the claim, so if claim is accepted, meaning H0 is rejected. So the Z lies within the critical range. Since it is a Right-tail test, Z is more than Z alpha.
See the bell shaped curve I drew, Z-test or Zcalc lies within the critical region...
Is it right to say that if H1 is rejected, Ho is not rejected and hence the z-test lie outside the critical region?
Yes
Then if I were to do a two tailed test, and using the old GC, do I use 0.05 or 0.95?
2 tail test have to half the significance level, ie each tail is now 0.025. Since now there is a left and right tail, referring to the left tail, you can use invNorm(0.025) which gives a negative value. The right tail value is just the positive of the same value coz is symmetrical...
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