alleryStart learning →A standardized exam has mean 500 and standard deviation 100. Tara scores 640. How many standard deviations above the mean is her score?
A1.64
B1.40
C0.64
D2.40
Answer & Solution
Correct answer: B. 1.40
1. The number of standard deviations from the mean is z = (value - mean)/standard deviation.
2. Substitute Tara's score: z = (640 - 500)/100.
3. That is 140/100 = 1.40 standard deviations above the mean.
4. So her score sits 1.4 standard deviations above average.
5. Option C, 0.64, divides the raw score by 1000 instead of measuring its distance from the mean.
_Source: OpenStax Introductory Business Statistics (CC BY 4.0), Ch 2 "Descriptive Statistics", section 2.7 Measures of the Spread of the Data_
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