A consumer organization inspecting new cars found that many had appearance defects (dents, scratches, paint chips, etc.). While none had more than three of these defects, 7% had exactly three, 11% exactly two, and 21% only one defect. Find the expected number of appearance defects in a new car and the standard deviation.

The expected number of appearance defects in a new car  = 0.64

standard deviation = 0.93(approximately)

Step-by-step explanation:

Given -

7% had exactly three, 11% exactly two, and 21% only one defect in cars.

Let X be no of defects in a car

P(X=3) = .07 , P(X=2) = .11 , P(X=3) = .21

P(X=0 ) = 1 - .07 - .11 - .21 = 0.61

The expected number of appearance defects in a new car =

E(X) = = = 0.64

 = variation of E(X) = =

 = = 0.8704

standard deviation  =   = = 0.93(approximately)

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