Unformatted text preview: test. What percent of people take more than 80 minutes to complete the test? What if our values are not exactly within one, two or three standard deviations from the mean? Probabilities for
these can still be found a number of ways, one of which we will explore in the next section. Using R, the
probability can be found with the command pnorm(X, µ, σ). Note that the command in R only gives the
probability that X is less than a given value. If we need to find the probability that X is greater than the given
value, we will need to subtract the answer from 1.
With the TI83 and TI84 calculator, the command is normalcdf(lower_limit, upper_limit, µ, σ).
Continuing the example above,
What is the probability that someone will take less than 45 minutes to complete the test? What is the probability that someone will take more than 30 minutes to complete the test? How long would it take someone to finish the test if they are in the top10% of the times?...
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 Spring '08
 HAFEEZ
 Normal Distribution, Standard Deviation

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