Good-Buy Electronics: You own a branch of Good-Buy Electronics and have been tol

Question

Good-Buy Electronics: You own a branch of Good-Buy Electronics and have been told by the manufacturer of Stevuski Televisions that only 5% of their brand of TVs die within one year. Last year, your branch sold 146 such televisions in July. One year later, 15 (about 10%) of them had been returned — dead.

(a) Assuming the 5% value quoted by the manufacturer was accurate, what is the mean number of TVs that die within one year in randomly samples of size 146? Round your answer to one decimal place.
=  

(b) What is the standard deviation? Round your answer to one decimal place.
=  

(c) You had 15 TVs die out of 146 (about 10%). With respect to the mean and standard deviation found in parts (a) & (b) respectively, what is the z-score for this many dead TVs? Round your answer to two decimal places.
z =  

(d) Assuming the 5% rate is accurate, would 15 dead TVs in a sample of 146 TVs be considered unusual?

Yes, that is an unusual number of dead TVs.No, that is not unusual.   

Explanation / Answer

= np =146*0.05=7.3

b) standard deviation =(np(1-p))1/2 =2.6

c)  z-score =(X-mean)/std deviation =(15-7.3)/2.6 =2.92

d)as z score is higher than 2 ; therfore

Yes, that is an unusual number of dead TVs

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