Homework Help: Statistics

Posted by Shams on Tuesday, October 26, 2010 at 6:31am.

A packaging device is set to fill detergent power packets with a mean weight of 5 Kg. The standard deviation is known to be 0.01 Kg. These are known to drift upwards over a period of time due to machine fault, which is not tolerable. A random sample of 100 packets is taken and weighed. This sample has a mean weight of 5.03 Kg and a standard deviation of 0.21 Kg. Can we calculate that the mean weight produced by the machine has increased? Use 5% level of significance.

Statistics - PsyDAG, Tuesday, October 26, 2010 at 10:56am
Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = ?(SEmean1^2 + SEmean2^2)

SEm = SD/?(n-1)

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to that Z score.

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