do #2 The weight of the American house mouse is normally distributed with mean o

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do #2

The weight of the American house mouse is normally distributed with mean of 13 ounces and standard deviation of 2.5 ounces. How much do the heaviest 10% of American house mice weigh? The IQs of Fijians are normally distributed with mean 100, and standard deviation of 15. What percent of Fijians have IQ less than 95? The IQs of Fijians are normally distributed with mean 100, and standard deviation of 15. If a random sample of 36 Fijians is selected, what is the probability that the mean IQ of this sample will be less than 95? We know that 10% of paper cuts become infected. What is the probability that of a random sample of 6 paper cuts that exactly 2 of these paper cuts become infected?

Explanation / Answer

as you asked answer question #2) here mean=13 and sd=2.5 ,

we use standard normal variate z=(x-mean)/sd

here we want to find z such that P(Z>z)=0.1 ( heaviest 10%)

or, P(Z<z)=1-P(Z>z)=1-0.1=0.9

corresponding z=1.28 ( using ms-excel command normsinv(.9))

now z=(x-mean)/sd

or, 1.28=(x-13)/2.5

or, x=13+1.28*2.5=16.2

so heavist 10% of mice would weight more than 16.2

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