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CA Foundation · Quantitative Aptitude · Theoretical Distributions

For a standard normal variate Z, which statement about the Z-table areas is correct?

P(Z < −a) = 1 − P(Z < a) is correct. The standard normal curve is symmetric about zero, so the left-tail area below −a equals the right-tail area above a. Half the total area lies on each side of zero.

  1. AP(Z < −a) = 1 − P(Z < a) for any aCorrect
  2. BP(Z > 0) = 1
  3. CP(Z < 0) = 0.25
  4. DP(Z < −a) = P(Z < a) for any a

Explanation

The standard normal curve is symmetric about 0, so the area to the left of −a equals the area to the right of a, which is 1 − P(Z < a). P(Z > 0) is 0.5 and P(Z < 0) is 0.5, so the other statements fail.

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