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Answer: 0.9608
Step-by-step explanation:
Given : A study of the amount of time it takes a mechanic to rebuild the transmission for a 2005 Chevrolet Cavalier shows that
Mean :
Standard deviation :
Sample size :
Let be the sample mean.
The formula for z-score in a normal distribution :
For
The P-value =
Hence, the probability that their mean rebuild time is less than 8.9 hours is 0.9608 .
Answer:
99.73% of bags contain between 62 and 86 chips .
Step-by-step explanation:
We are given that the number of chips in a bag is normally distributed with a mean of 74 and a standard deviation of 4.
Let X = percent of bags containing chips
So, X ~ N()
The standard normal z score distribution is given by;
Z = ~ N(0,1)
So, percent of bags contain between 62 and 86 chips is given by;
P(62 < X < 86) = P(X < 86) - P(X <= 62)
P(X < 86) = P( <
) = P(Z < 3) = 0.99865 {using z table}
P(X <= 62) = P( <=
) = P(Z <= -3) = 1 - P(Z < 3)= 1 - 0.99865 = 0.00135
So, P(62 < X < 86) = 0.99865 - 0.00135 = 0.9973 or 99.73%
Therefore, 99.73% of bags contain between 62 and 86 chips .