Área 9 perímetro 20 what is the leigh and width
1 answer:
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Answer:
4.924 years
Step-by-step explanation:
Lets denote X the lifetime of a tv tube (In years). X has distribution , with
unknown.
We know that P(X < 4) = 0.2. Using this data, we can find the value of throught standarization.
Lets call the standarization of X. Z has distribution N(0,1), and its cummulative function,
is tabulated. The values of
can be found in the attached file.
The value q such that doesnt appear on the table. We can find it by using the symmetry of the normal density function. The opposite of q, -q must verify that
, hence -q must be equal to 0.84. Thus, q = -0.84
But this value of q should match with the number , so we have
Thus, the expected lifetime of TV tubes is 4.924 years.
I hope this works for you!