# Data File 3 - Northcentral University Data File...

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Northcentral University Data File 3/Statistics in Educational Research Data File 3 Show all work Chapter Five 1) If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours? 2) The lifetimes of light bulbs of a particular type are normally distributed with a mean of 370 hours and a standard deviation of 5 hours. What percentage of bulbs has lifetimes that lie within 1 standard deviation of the mean on either side? 3) The amount of Jen’s monthly phone bill is normally distributed with a mean of \$60 and a standard deviation of \$12. Fill in the blanks: 68% of her phone bills are between \$______________ and \$______________. 4) The amount of Jen’s monthly phone bill is normally distributed with a mean of \$50 and a standard deviation of \$10. Find the 25 th percentile. 5) The diameters of bolts produced by a certain machine are normally distributed with a mean of 0.30 inches and a standard deviation of 0.01 inches. What percentage of bolts will have a diameter greater than 0.32 inches?

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