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99% confidence interval


New member
Oct 23, 2009
Too much Cellulose? Excess cellulose in alfalfa reduces the relative feed value of the product that will be fed to dairy cows. if the cellulose content is too high, the price will be lower and the producer will have less profit. alfalfa crops for which the mean cellulose content exceeds 140 mg/g is considered of inferior quality. as part of a quality control process, a sample of 36 alfalfa cutting are tested: the average cellulose content for the sample was x-bar= 145 mg/g and the standard deviation of the measurements was 8 mg/g. construct a 99% confidence interval to estimate the mean cellulose content for the alfalfa crops from which the sample was taken. based on your confidence interval, what would you conclude about the quality of the crops in terms of its cellulose content?

I got confidence intervals of 196.8 and 189.9. Are these correct? I'm just not really sure of the steps involved or how to estimat the mean cellulose content.
I used 145 +or- 2.576(8/Sq root of 36)
xbar = 145
st deviation = 8
n= 36

I also never really know when to stop. i took stats a while ago and barely got thru the class. my current prof. has a very thick accent and moves very quickly thru the problems assuming we just "know" a lot of minor details. all the examples we have are for 95% intervals.
Where do i go from here?


Full Member
Dec 14, 2005
You are done if you made no arithmetic mistake.