Asked by Anonymous
Suppose the final exam scores in a large class is symmetric mound shaped with a mean of 70 points and standard deviation of 10 points. The percentage of students in the class who receive more than 60 points is approximately
Answers
Answered by
MathGuru
Use z-scores.
Formula:
z = (x - mean)/sd
x = 60
mean = 70
sd = 10
Substitute into the formula and find z. Use a z-distribution table to find the probability. Convert to a percent.
I hope this will help get you started.
Formula:
z = (x - mean)/sd
x = 60
mean = 70
sd = 10
Substitute into the formula and find z. Use a z-distribution table to find the probability. Convert to a percent.
I hope this will help get you started.
Answered by
MathMate
60% is 70%-10% (1 standard deviation).
Look up a normal distribution table (or
http://www.mathsisfun.com/data/standard-normal-distribution-table.html
)
to find that at Z=1 (1 standard deviation) below mean is (0.5)-0.3413=0.1587
So 15.87% of the class has (70-10)=60% or less. So how many are above 60?
Look up a normal distribution table (or
http://www.mathsisfun.com/data/standard-normal-distribution-table.html
)
to find that at Z=1 (1 standard deviation) below mean is (0.5)-0.3413=0.1587
So 15.87% of the class has (70-10)=60% or less. So how many are above 60?
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