Problem #8 A survey indicates that 40% of households in the USA own CD players F

Question

Problem #8 A survey indicates that 40% of households in the USA own CD players From a random sample of 12 households in the USA find the probability that the number of households who own CD players is: a) at least 8 b) between 4and 7, at most 5 Problem #9 A lady has 6 cats. Each cat has a 0.60 probability of climbing into the chair in which the lady is sitting, independently of how many cats are already in the chair with the lady. Find: a) The probability of having no cats in the chair with the lady The probability of having at least 4 cats in the chair with the lady The probability of having at most 3 cats in the chair with the lady c) Problem #10 A teacher gives a test to a large class; and the grades are closely approximated by a Normal Curve with a mean of 74 and a standard deviation of 6 The teacher assigns a grade of A to the top 8% of class and a grade of F to the bottom 8%. Find the cutoff point for a grade of A and a grade of F.

Explanation / Answer

a) 0.057309 by using BINOM.DIST.RANGE(12,0.4,8,12)

P(X=>8)=P(X=8)+P(X=9)+P(X=10)+P(X=11)+P(X=12)

b) 0.717352 by using BINOM.DIST.RANGE(12,0.4,4,7)

c) 0.66520 by using BINOM.DIST.RANGE(12,0.4,0,5)

10 )

to be in top 8 %

mu= 74

sigma= 6

X= unknown

probability= 0.92

z-score for probability=1.40507

Z=(X-mu)/sigma

x=(mu+Z*sigma)

x= 82.4304

minimum score to get A is 82.43

to be in bottom 8%

mu= 74

sigma= 6

X= unknown

probability= 0.08

z-score for probability=-1.4050

Z=(X-mu)/sigma

x=(mu+Z*sigma)

x= 65.5695

to be in F grade score must be less than 65.57

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