To calculate: The percentage of observations that lie within one-half of a standard deviation from the mean.
The percentage of observations that lie within one-half of a standard deviation from the mean is 38%.
Given:
The distribution is
Concept used:
In a normal distribution, the percentage of data within one standard deviation of the mean is about 68%, the percentage of data within two standard deviations of the mean is about 95%, and the percentage of data within three standard deviations of the mean is about 99.7%. The Z score of a data value is the number of standard deviations from the mean and is calculated using the formula
where
The probability between any two Z scores can be calculated using the following function in a graphical calculator. “Normal CDF(lower boundary, upper boundary)”
Calculation:
The given data points are one-half of a standard deviation from the mean, so the Z scores are -0.5 and 0.5.
The upper boundary is 0.5 and the lower boundary is -0.5.
Using the function in calculator NORMAL CDF (-0.5, 0.5),
Conclusion:
The percentage observations lie within one-half of a standard deviation from the mean is about 38%. Option C is correct.
Chapter 10 Solutions
PRECALCULUS:GRAPHICAL,...-NASTA ED.
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