stats need help

Violence in School, I An SRS of 400 American adults is asked “What do you think is the most serious problem facing our schools?” Suppose that in fact 40% of all adults would answer “violence” if asked this question. The proportion p of the sample who answers “violence” will vary in repeated sampling. In fact, we can assign probabilities to values of p using the normal density curve with mean 0.4 and standard deviation 0.023. Use the density curve to find the probabilities of the following event:

a.At least 45% of the sample believes that violence is the school’s most serious problem.


b.Less than 35% of the sample believes that violence is the most serious problem.


c.The sample proportion is between 0.35 and 0.45.

asked by Jaz
  1. .45 is .05 away from the mean or .05/.023 = 2.17 standard deviations away from the mean. Your stats book should have a cumulative normal distribution table. Look up 2.17. I get .9850, meaning that the probability of observing a sample where more than 45% is 1-.985 = .015=1.5%

    .35 is also 2.17 standard deviations from the mean. Take it from here.

    posted by economyst
  2. so for c. do i subtract the amounts of the two

    posted by jaz

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