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Midterm #3  Spring 2004
1. Giraffes have long tongues, averaging
μ
= 15.8 inches, with standard deviation
σ
= 1.8 inches.
The
distribution of lengths is normal.
Acacia will get a simple random sample of 80 giraffes and measure
their tongues.
a. Find the chance that the average length of the tongues of the giraffes in the sample is more
than 16 inches.
b. Pick a phrase to complete the sentence:
If Acacia were to get a bigger sample, the probability
in question a.
..
...would be bigger.
...would be smaller
...would stay the same.
...might change, but it is not possible to say how.
c.
Did you need to know that the population had a normal distribution to answer question a?
Answer “yes” or “no” and explain your answer.
2. Dusty wanted to estimate the average number of hours people spend cleaning house per week.
He
rented time on a secret spy satellite and observed the times spent by a random sample of 12 people.
He found that the average time was 200 minutes, and the standard deviation of the sample was s = 54
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 Spring '08
 Staff
 Statistics, Probability, Standard Deviation

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