The Mean Life of a Particular Brand of Light Bulb

question 4

Multiple Choice

The mean life of a particular brand of light bulb is 1200 hours and the standard deviation is 50 hours.We can conclude that at least 75% of this brand of bulbs will last between _______.

• A)1100 and 1300 hours
• B)1150 and 1250 hours
• C)1050 and 1350 hours
• D)1000 and 1400 hours
• E)950 and 1450 hours