Researchers have developed a filament that should add to the life expectancy of light bulbs. A sample of n=100 bulbs is prepared using the new...

Researchers have developed a filament that should add to the life expectancy of light bulbs. A sample of n=100 bulbs is prepared using the new filament. The average life for this sample is σ =15.

a. Use the sample data to make a point estimate of the mean life expectancy for the new filament.

b. Make an interval estimate so that you are 80% confident that the true mean is in your interval.

c.make an interval estimate so that you are 99% confident that the true mean is in your interval.