The life expectancy of a fluorescent light bulb is given by the number of hours that it will burn. From the following frequency distribution, find the sample standard deviation s (in h). (Use the mean value 2,220.6 h to calculate the sample standard deviation rounded to the nearest whole number.)
Extracted text: Product xf Life of bulb Midpoint Frequency f (hours) -0.5-499.5 249.5 499 499.5-999.5 749.5 11 8,244.5 999.5-1,499.5 1,249.5 13 16,243.5 1,499.5-1,999.5 1,749.5 16 27,992 1,999.5-2,499.5 2,249.5 28 62,986 2,499.5-2,999.5 2,749.5 32 87,984 2,999.5-3,499.5 3,249.5 13 42,243.5 3,499.5-3,999.5 3,749.5 22,497 S =