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PRGirl PRGirl
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9 years ago
A set of final exam scores in an organic chemistry course was found to be normally distributed, with a mean of 73 and a standard deviation of 8. What is the probability of getting a score of 68 or less on this exam? Place your answer, rounded to 4 decimal places in the blank. For example, 0.3456 would be a legitimate entry.
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AlexxAlexx
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PRGirl Author
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9 years ago
Quote from: Alexx (9 years ago)
You will probably use the z-test (or whatever it is called).

We have: z= (x-μ)/σ      μ is the mean, σ is standard deviation.
z= (x-μ)/σ = (68 - 73)/8 = -5/8 = -0,625

Now, the problem is that I don't have such accurate tables to find 4 decimals. The most presice answer I could find (using an online calculator) was 0,266. (see attachment). I guess you have the nessecary tables to find the answer, knowing that z=-0,625.

Correction: It seems that the calculator I used ( http://www.mathcracker.com/normal_probability.php ) is showing results with 4 decimals. It just happened that the answer is 0,266. Check your tables to be sure though.

Wow, thank you so much you totally helped me on this. I found another calculator that gave me the 4 digits its here...

http://www.mathportal.org/calculators/statistics-calculator/normal-distribution-calculator.php

I was able to get the right answer because of your help. Thank you so much!
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