Data Analysis of Fish Weight: Finding % & # within 1 SD

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Scharles
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This question involves a table...

The weight of 150 fish in a pond are shown in the table below.


Weight of fish (in gm) Number of fish,f
10-19 6
20-24 12
25-29 30
30-34 50
35-39 32
40-59 20

(a) Calculate the percentage of fish with weights between 28 and 45 gm.
(b) Find the number of fish that has the weight within one standard deviation from the mean.

(Given mean and standard deviation are 32.9 and 8.403)

The answers given are 64.67% and 91...
 

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Just a quick observation... you can say what the highest possible percentage of fish in a certain range is easily just by adding them up and dividing by the total, but in order to narrow it down you'd need to get your hands dirty. Actually, you can't really tell the probabilities associated with the s.d. without knowing the dist (? or can you?). Maybe try Chebysheff's Theorem.