Question

An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 45 hours. If a sample of 35 bulbs has an average life of 710 ​hours, find a 96​% confidence interval for the population mean of all bulbs produced by this firm.

Answer 1

[693,38:725,62]hs

Explanation:

Hello!

Your study variable is X: the lifespan of a light bulb. This variable is said to have an approximately normal distribution.

X≈N(μ;σ²)

Were

μ= populatiom mean

σ= 45 hs standard deviation

A sample of n= 35

To estimate the population mean with a confidence interval you have to use the Z statistic:

X{bar} ±
`Z_(1-\alpha /2)`*(σ/√n)

`Z_(1-\alpha /2) = Z_(0.98) = 2.054`

710 ± 2.054*(45/√35

[693,38:725,62]hs

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