Quantitative Research

What is the probability of 59 if the mean is 60 and the standard deviation is 7?

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1. If you have a discrete distribution, i.e. the values are integers, then the probability of 59 would be the equivalent of the group 58.5 to 59.5 in a continuous distribution.
58.5 corresponds to z1=((μ-58.5)/σ) and 59.5 to z2=((μ-59.5)/σ).
Assuming the distribution is normal, look up the z-tables to find the one-tail probabilities of z1 and z2. The difference between z1 and z2 will be the probability of getting between 58.5 and 59.5.

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2. The average commute time via train from the Chicago O'Hare Airport to downtown is 60 minutes with a standard deviation of 15 minutes. Assume that the commute times are normally distributed. What proportion of commutes would be:
longer than 80 minutes?
less than 50 minutes?
between 45 and 75 minutes?

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posted by Tina
3. Quantitative Research - Tina, Saturday, May 28, 2011 at 7:52pm
The average commute time via train from the Chicago O'Hare Airport to downtown is 60 minutes with a standard deviation of 15 minutes. Assume that the commute times are normally distributed. What proportion of commutes would be:
longer than 80 minutes?
less than 50 minutes?
between 45 and 75 minutes?

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2. 👎 0
posted by sharon

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