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Probability function

David Harper CFA FRM

David Harper CFA FRM
Staff member
Hi @Pooja kataria you can't retrieve these on the TI BA II+ calculator, you need to use the Z lookup table which is provided. See below, this is from GARP Part 1 Practice Paper. I've pointed in red (top square) where indicates: Pr(Z < -2.33) = 0.0099 which is the nearest to 1.0%, so this represents Pr(Z < -2.33) ≈ 1.0%. In this way, N^(-1)(0.010) = -2.33 where 0.010 is the cumulative probability and -2.33 is the standard normal quantile. Although this particular quantile should be memorized along with +/- 1.645 @ 95.0%. And the normal is symmetrical so we need to know and be facile with the symmetrical fact that N(-Z) = 1 - N(Z) such that N(2.33) = 1 - N(-2.33) = 1 - 1.0% = 99.0%. Notice GARP's table only shows the left side!