The average life of light bulbs produced by saba electric co. is believed to be normally distributed with the mean service life of 950 hours and a standard deviation of 100 hours. a random sample of 100 bulbs is tested and it has a mean life of 930 hours. can it be concluded that the mean service life of the bulbs is less than the expectation at significant level of 0.01?

We cannot conclude that the mean life of the bulbs is less than 950h.

Step-by-step explanation:

Be,

Sample mean (MX) = 930h

Population standard deviation (sigma) = 100h

Sample size (n) = 100

Significance level (alpha) = 0.01

Null hypothesis (H0): Mu = 950

Alternative hypothesis (Ha): Mu <950

Population mean in the null hypothesis (Mu0) = 950

Critical value (Z-alpha) = -2.32635.

The test statistic in this case is given by:

Since is greater than Z-alpha, it is decided not to reject H0. That is, we cannot conclude that the average life of the bulbs is less than 950h.

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