Over the past three years, Freddie's car maintenance sessions cost $250 , $270 , and $260 What is the standard deviation? Use the following formula for Standard Deviation: sigma is equal to square root of the fraction with numerator the sum from i is equal to 1 to n of open paren x sub i minus m close paren squared and denominator n end root where x sub i is each data point, and n is the number of data points.
The mean of $250, $270, and $260 is $260. Their squared differences from the mean are 100, 100, and 0, so the variance using the given formula is (100 + 100 + 0) ÷ 3 = 66.67. Taking the square root gives about 8.16, so the standard deviation is choice B, 8.16.
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