Z = (mean1 - mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√n
If only one SD is provided, you can use just that to determine SEdiff.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.
An engineering company believes it has developed a faster way to complete the assembly of an industrial machine. The present process takes an average of 6.5 hours to complete and the times it takes to complete the process are approximately normally distributed. If the mean time for the new process is faster at the 0.05 level of significance, the engineering company will present the new process to their clients. Otherwise, the company will do further research. The company assembles a number of machines using the new process and randomly selects 17. The assembly times for the 17 machines in the sample are shown. Perform a hypothesis test showing your work.
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1 answer