Bright Bulb light bulb company is planning a study to assess the average life expectancy of their light bulbs. They know the standard deviation is σ = 400 hours. They want a 95% confidence interval with a margin of error of 50 hours. What sample size do they need?

Sample size = 246 .

Step-by-step explanation:

We are given that Bright Bulb light bulb company is planning a study to assess the average life expectancy of their light bulbs. For this they know;

Standard deviation, = 400 hours         Confidence interval = 95%

Margin of error = 50 hours

We know that Margin of error formula is given by;

    Margin of Error =   where = 5%

                   50       =  1.96 *  

                       =   = 15.68

                      n  =   = 245.86 ≈ 246

So, sample size needed will be 246 bulbs.

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step-by-step explanation: