In this item, we have the mean incubation period of 23 days and the standard deviation is 22 days. We use z-score to determine the unknown in each of the items.
(a) less than 21 days.
z-score = (23 - 21) / 22 = 1/11
This translates to a percentage of 53.6%
(b) z-score for 19 days.
z-score = (23 - 19) / 22 = 2/11
This translates to a percentage of 57.2%.
z-score for 23 days.
z-score = (23 - 23)/ 22 = 0
This translates to a percentage of 50%.
The difference between the two numbers is only 7.2%
(c) z-score of 25.
z-score = (23 - 25)/ 22 = -1/11
This translates to a percentage of 42.3%.
Then, subtract this value from 100 to give us the final answer of 57.2%.
Notice, the third decimal place is 9 in 3.469644...
and after the 469 there's a 6, that means we can round that 469 to a 470
3.470.
Total earnings = 650 + 530 + 52 - 28 - 75 = $1129
Goal = $1100
Exceeded by = $1129 - $1110 = $9.
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Answer: The school exceed their goal by $9.
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