SOLUTION: Could you please tell me what formula to use to solve this problem? A study found that the mean migration distance of the green turtle was 2200 kiloeters and the standard deviatio

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Question 1008936: Could you please tell me what formula to use to solve this problem? A study found that the mean migration distance of the green turtle was 2200 kiloeters and the standard deviation was 625 kilometers. Assume that the distances are normally distributed. Seventy % of all the distances traveled were greater than how many kilometers? I would appreciate help with this one.
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
A study found that the mean migration distance of the green turtle was 2200 kiloeters and the standard deviation was 625 kilometers. Assume that the distances are normally distributed. Seventy % of all the distances traveled were greater than how many kilometers?
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Sketch a normal curve
Put 2200 km in the middle (it is the mean)
Keep in mind the std = 625 km.
The numbers to the right are greater than the numbers to the left.
Shade 70% of the area under the curve starting at the right end
and moving to the left.
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Find that left border value in ft.
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Since 70% is to the right of the border, 30% is to the left.
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Using a TI-84 calculator the z-value there is invNorm(0.30) = -0.5245
That means your border is 0.5245 stamdard deviations to the LEFT of the mean.
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Ans: 2200-0.5245*625 = 1872.25 ft
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Cheers,
Stan H.
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