Hypothesis Testing (easy for you, hard for me!)
Message posted by Jamie (via 209.254.185.155) on November 3, 2001 at 9:14 PM (ET)

Here is the question I am posed: "A cheesemaker buys milk from several suppliers as the raw material for his cheese. He suspects that some producers are adding water to their milk to increase their profits. Excess water can be detected by determining the freezing point of the milk. The freezing temp. of natural milk varies normally, with a mean of -.545 Celsius and a standard deviation of .008 C. Added water raises the temp toward 0.0C, the freezing point of water. The cheesemaker's lab manager measured the freezing temp in five consecutive lots of milk from one producer. The mean measurement is -.538 C."
Now I am asked to state a Null and Alternative hypothosis for this problem, specify the test statistic and find the standard deviation and standard error. I have been pouring over my text and notes all night, but am a little stumped. If anyone could help, I would REALLY appreciate it! Thanks so much!

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Re: Hypothesis Testing (easy for you, hard for me!)
Message posted by Tomi (via 154.32.143.41) on November 3, 2001 at 11:18 PM (ET)

Null Hyp: Mean = -.545
Alt Hyp:Mean > -.545

Test statistic: z score = (observed value - mean under Null Hyp)/(standard error) = (-.538 - -.545)/(0.008/sqrt(5))

Check if z-score is greater than critical value: probably go for top 5% of normal => critical value = 1.645