The line plots show the number of hours two different age groups of teenagers spent online the previous week.

1 answer:

4 0

The range of the top plot, hours spent by 13-15 year olds, is found by subtracting the highest value, 34, and the lowest value, 21. 34-21=13.
The mean of the top plot is found by adding together all of the data points and dividing by 10 (the number of data points):
$\frac{21+24+26+27+27+28+28+28+31+34}{10}=\frac{274}{10}=27.4$

The range of the bottom plot, minutes spent online by 16-18 year olds, is found by subtracting the highest value, 36, and the lowest value, 12. 36-12=24.
The mean of the bottom plot is found by adding together all of the data points and dividing by 11 (the number of data points):
$\frac{12+21+27+28+28+28+28+30.5+34+35+36}{11}=\frac{307.5}{11} \approx27.95$

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Z = (X-Mean)/SD
z1 = (165 - 150)/15 = +1 
z2 = (135 - 150)/15 = - 1 
According to the Empirical Rule 68-95-99.7 
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100% - 68% = 32% 
The remaining 32% is equally distributed below z = - 1 and z = +1 
32%/2 = 16%

Therefore,

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b) Number of men weighing less than 135 pounds = 16% of 1000 = 160

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