Question

Find z such that 7.8% of the standard normal curve lies to the left of z. z = ______. Find z such that 7.4% of the standard normal curve lies to the right of z. z = ______. Find the z value such that 81% of the standard normal curve lies between −z and z. (Round your answer to two decimal places.) z = ______.

Answer 1

Find z such that 7.8% of the standard normal curve lies to the left of z

Z value at 0.078=    -1.42 (excel formula =NORMSINV(0.078) )

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Find z such that 7.4% of the standard normal curve lies to the right of z

area to the left = 1 - 0.074 = 0.926

Z value at 0.926=1.45 (answer) (excel formula =NORMSINV(0.926) )

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Find the z value such that 81% of the standard normal curve lies between −z and z

middle proportion=0.81

proportion left 0.19is equally distributed both left and right side of normal curve

z value at0.095= ±1.31    (excel formula =NORMSINV(0.19/ 2 ) )

so, value of z = 1.31

-z = -1.31