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October 2011 Paper Q8 (ii) Part b

S

studyc

Member
Hi,

In the solutions to the question it states 2x[P(Z<0.63246)-0.5]

Why do we minus the 0.5 here?

Thanks
 
studyc said:
Hi,

In the solutions to the question it states 2x[P(Z<0.63246)-0.5]

Why do we minus the 0.5 here?

Thanks
Click to expand...

Because it means when multiplied out we get 2P(Z<0.63246) - 1
which is a rearrangement of:

P(-0.63246 < Z < 0.63246) = P(Z < 0.63246) - P(Z < -0.63246)

= P(Z < 0.63246) - [1 - P(Z < 0.63246)]
 
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