08: Binomial to Normal

I'm having problems finding solutions for all parts of problem #2.

I think you calculate the z score and then cross reference that with the tables pdf somehow.



  • edited June 19

    Disregard. I figured it out. I was looking up the percentage first instead of the z score. I'm still unclear how you would figure out the probability for 10 random people though.

  • Hi Jordan. I don't know if you still need this info, but here it goes.
    This is my question 2b:
    Scores for men on the verbal portion of the SAT-I test are normally distributed with a mean of 509 and a standard deviation of 112.
    (b) If 19 men are randomly selected, find the probability that their mean score is at least 572.5.

    I first found the z score with: z=(x-xbar)/(sigma/sqrt(n)) which for me is:

    z= (572.5-509)/(112/sqrt(19))
    z= 2.47, looking this up in table yielded 0.9932 -> (1-0.9932)=0.0068

    The probability is 0.0068.

    Hope this helps

  • Thanks Beau - that worked.

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