Question

The mean value of land and buildings per acre from a sample of farms is $1800, with a standard deviation of $300.

The data set has a bell-shaped distribution. Using the empirical rule, determine which of the following farms, whose
land and building values per acre are given, are unusual (more than two standard deviations from the mean). Are any
of the data values very unusual (more than three standard deviations from the mean)?

$1625 $2493 $1521 $615 $1656 $1664

Which of the farms are unusual (more than two standard deviations from the mean)? Select all that apply.

A. $615
B. $1656
C. $1625
D. $2493
E. $1521
F. $1664

Answer 1

Answer: Using the empirical rule, if the distribution is bell-shaped, we know that about 68% of the data falls within one standard deviation of the mean, about 95% of the data falls within two standard deviations of the mean, and about 99.7% of the data falls within three standard deviations of the mean.

To determine which of the farms are unusual (more than two standard deviations from the mean), we need to calculate the lower and upper bounds for two standard deviations from the mean:

Lower bound = Mean value - (2 * Standard deviation) = $1800 - (2 * $300) = $1200

Upper bound = Mean value + (2 * Standard deviation) = $1800 + (2 * $300) = $2400

So, any data value outside this range is considered unusual. Therefore, the farms that are unusual are:

$2493 (more than two standard deviation from the mean)

None of the data values are very unusual (more than three standard deviations from the mean)

Explanation:

Answer 2

A and D

Explanation:

The Empirical Rule states that for a bell-shaped distribution, approximately 68% of the data falls within one standard deviation of the mean, approximately 95% falls within two standard deviations of the mean, and approximately 99.7% falls within three standard deviations of the mean.

Given that the mean value of land and buildings per acre from the sample of farms is $1800 and the standard deviation is $300, we can use this information to determine which farms are unusual (more than two standard deviations from the mean).

A. $615 is unusual, it is more than two standard deviations from the mean, which is $1800. $615 is $1185 less than the mean. Since it is more than $600 less than the mean, it is more than two standard deviations from the mean.

B. $1656 is not unusual, it is less than 2 standard deviations from the mean.

C. $1625 is not unusual, it is less than 2 standard deviations from the mean.

D. $2493 is unusual, it is more than two standard deviations from the mean, which is $1800. $2493 is $693 more than the mean. Since it is more than $600 more than the mean, it is more than two standard deviations from the mean.

E. $1521 is unusual, it is more than two standard deviations from the mean, which is $1800. $1521 is $279 less than the mean. Since it is more than $600 less than the mean, it is more than two standard deviations from the mean.

F. $1664 is not unusual, it is less than 2 standard deviations from the mean.

None of the data values are very unusual (more than three standard deviations from the mean).

So the farms that are unusual (more than two standard deviations from the mean) are A and D.