Probability Question. Normally distributed

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The discussion revolves around a probability question related to a plant extract tested for leukemia treatment, specifically focusing on the amount of collagen, which is normally distributed with a mean (μ) of 71 grams per milliliter and a standard deviation (σ) of 8.5 grams per milliliter. Participants calculated the probability of collagen amounts being greater than 65 grams per milliliter (0.761) and less than 84 grams per milliliter (0.937). A question arose regarding the percentage of compounds within one standard deviation of the mean, which remains unanswered. One user expressed frustration over their attempts to solve the problem using the Z-score formula, indicating confusion about the values used in their calculations. The thread highlights the complexities of applying normal distribution in practical scenarios.
mah062
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1) (1 pt) The extract of a plant native to Taiwan has been tested as a possible treatment for Leukemia. One of the chemical compounds produced from the plant was analyzed for a particular collagen. The collagen amount was found to be normally distributed with μ=71 and σ= 8.5 grams per mililiter.

a) What is the probability that the amount of collagen is greater than 65 grams per mililiter?
Answer: 0.761

b) What is the probability that the amount of collagen is less than 84 grams per mililiter?
Answer: 0.937

c) What percentage of compounds formed from the extract of this plant fall within 1σ of μ(Not sure if this is the right symbol but it's supposed to stand for the mean)?
Answer: ?

2) Relevant equations...
P([(x-μ)/σ]<Z<[(x-μ)/σ])

Normally Distributed...
f(x)=[1/(σ√(2pi))][e^(-0.5[(x-μ)/σ]^2)]



3. The Attempt at a Solution .
I've tried everything I can think of. I used P([(62.5-71)/8.5]<Z<[(79.5-71)/8.5]) but it was wrong. I've attempted it 28 different ways. Can anyone help me? Thanks!
 
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mah062 said:
1) (1 pt) The extract of a plant native to Taiwan has been tested as a possible treatment for Leukemia. One of the chemical compounds produced from the plant was analyzed for a particular collagen. The collagen amount was found to be normally distributed with μ=71 and σ= 8.5 grams per mililiter.

a) What is the probability that the amount of collagen is greater than 65 grams per mililiter?
Answer: 0.761

b) What is the probability that the amount of collagen is less than 84 grams per mililiter?
Answer: 0.937

c) What percentage of compounds formed from the extract of this plant fall within 1σ of μ(Not sure if this is the right symbol but it's supposed to stand for the mean)?
Answer: ?

2) Relevant equations...
P([(x-μ)/σ]<Z<[(x-μ)/σ])

Normally Distributed...
f(x)=[1/(σ√(2pi))][e^(-0.5[(x-μ)/σ]^2)]



3. The Attempt at a Solution .
I've tried everything I can think of. I used P([(62.5-71)/8.5]<Z<[(79.5-71)/8.5]) but it was wrong. I've attempted it 28 different ways. Can anyone help me? Thanks!

In your expression above, where does the number 62.5 come from? Where does the 79.5 come from? Why do you have two inequalities on Z?

RGV
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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