20th percentile of Mrs. Starnes’s Sudoku times for easy puzzles.
Answer to Problem 63E
20th percentile is 4.544 minutes.
Explanation of Solution
Given information:
Mean,
Standard deviation,
Calculations:
The data value represented by the xth percentile has x% of the data values below it.
That implies
The data value represented by the 20th percentile has 20% of the data values below it.
Now,
Find the z − score corresponding the
Note that
The closest probability would be 0.2005 that lies in the row -0.8 and in the column .04 of the normal probability table.
Then
The corresponding z − score,
In order to find xthpercentile, calculate the z − score
Equate the above two expressions:
Multiply both sides by 0.9:
Add 5.3 to both sides:
That becomes
Thus,
20th percentile will be 4.544 minutes.
Chapter 2 Solutions
PRACTICE OF STATISTICS F/AP EXAM
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