# stats a level

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#1
P(−a<Z <a)=0.40 ⇒
P(−a<Z <0)=0.20 ⇒
P(−a < Z) = 0.30
⇒ −a = −0.52440...
⇒ a = 0.5244 (4 d.p.)

this is a standard normal distribution so Z-N(0,1^2)

i understand up until P(−a<Z <0)=0.20 , but then hpow does the 0.20 change to 0.3??
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3 weeks ago
#2
The inequality also flips. I guess it should be P(Z<-a) = 0.3? But it would help to see the original.
Can you sketch a bell curve and mark/shade the regions?
The total area under the curve is 1
Last edited by mqb2766; 3 weeks ago
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