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    Please do Help me

    1. Blood pressure is described by two numbers: systolic pressure and diastolic pressure (measured in mm of Hg). A study showed systolic pressure to be normally distributed with a mean of 125 and a standard deviation of 15, and the diastolic pressure to be normally distributed with a mean of 84 and a standard deviation of 9. Two study participants are randomly selected and their blood pressures are measured. The first participant had a systolic reading of 100 mm of Hg, while the second had a diastolic reading of 75 mm of Hg. Which participant had a lower reading with regard to the study population?


    8. The annual number of earthquakes, the world over, is a random variable having approximately a normal distribution with m=20.8(mutte symbol). What is the standard deviation of this distribution if the probability is 0.40 that there will be less than 15 earthquakes?
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  2. #2
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    Quote Originally Posted by hidaja16 View Post
    1. Blood pressure is described by two numbers: systolic pressure and diastolic pressure (measured in mm of Hg). A study showed systolic pressure to be normally distributed with a mean of 125 and a standard deviation of 15, and the diastolic pressure to be normally distributed with a mean of 84 and a standard deviation of 9. Two study participants are randomly selected and their blood pressures are measured. The first participant had a systolic reading of 100 mm of Hg, while the second had a diastolic reading of 75 mm of Hg. Which participant had a lower reading with regard to the study population?


    8. The annual number of earthquakes, the world over, is a random variable having approximately a normal distribution with m=20.8(mutte symbol). What is the standard deviation of this distribution if the probability is 0.40 that there will be less than 15 earthquakes?
    The help given here http://www.mathhelpforum.com/math-he...-graduate.html is relevant. Read it first.

    1. Convert X = 100 into a z-score: Z = \frac{100 - 125}{15} = \, ....

    Convert Y = 75 into a z-score: Z = \frac{75 - 84}{9} = \, .... .

    Which z-score is lower .....?

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    8. Pr(X < 15) = 0.40.

    Now get the value of z* such that Pr(Z < z*) = 0.40.

    Then z^* = \frac{15 - 20.8}{\sigma}.

    Solve for \sigma.
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