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The results of a chemistry examination are normally distributed with a mean score of 56 and a standard deviation of 12.
What is the percentage probability that a student will score more than 80?the answer is
28%
Z-score = (x -?)/?
Therefore: (80 –56)/12 = 2
From the normal distribution table, 2 = 0.4772
To find the probability of scoring more than 80: 0.5 –0.4772 = 0.0228 or 2.28% as a %.where does the 0.5 come from? is it always 0.5 in these questions?
The 0.5 is because in a normal distribution always 50% (or 0.5) are above the mane and 0.5 are below the mean, because it is symmetrical.
I do suggest that you watch my free lectures on this where I do explain it.
The lectures are a complete free course for Paper MA and cover everything needed to be able to pass the exam well.
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