SOLUTION: 3. The lifetimes of a colour TV picture tube is normally distributed, with a mean of 8 yrs and a standard deviation of 2 years. (i) What is the probability that a picture tube wi

Algebra ->  Probability-and-statistics -> SOLUTION: 3. The lifetimes of a colour TV picture tube is normally distributed, with a mean of 8 yrs and a standard deviation of 2 years. (i) What is the probability that a picture tube wi      Log On


   

Question 853777: 3. The lifetimes of a colour TV picture tube is normally distributed, with a mean of 8 yrs and a standard deviation of 2 years.
(i) What is the probability that a picture tube will last more than 10 yrs?
(ii) If the firm guarantees the picture tube for 4 yrs, what percentage of the tubes sold will have to be replaced?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

mean of 8 yrs and a standard deviation of 2 years.

(i)Using TI: The syntax is normalcdf(smaller, larger, µ, σ).

Note: The -9999 is used as the smaller value to be at least 5 standard deviations from the mean.

P(x > 10) =  1 - normalcdf(-9999,10, 8,2)

(ii) 

P(x < 4) = normalcdf(-9999,4, 8,2)

0r

P(P(x > 10) = 1 - NORMSDIST(1) =  1 - .8413 = .1587

P(x < 4) =  =  NORMSDIST(-2) = .0028     .28% will have to be replaced