While you are working at your desk, you smell fire. Within seconds, the fire alarm sounds. What should you do?
2 answers:
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Answer:
option d) approximately 84%
Explanation:
Data provided in the question:
Mean, m = $92
Standard deviation, s = $13
Now,
we have to calculate percentage of homes will have a monthly utility bill of more than $79 i.e P(X > 79)
also,
P( X > 79) = 1 - P( X < 79)
Z-score for (X = 79 ) =
Z =
or
Z = -1
From the standard Z value vs P table, we have
P( Z < -1 ) = 0.1587
Thus,
P( X < 79) = P( Z < -1 ) = 0.1587
therefore,
P(X > 79) = 1 - 0.1587
or
P(X > 79) = 0.8413
or
= 0.8413 × 100%
= 84.13%
Hence,
option d) approximately 84%