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Is a measure of 25 inches​ "far away" from a mean of 16 ​inches? As someone with knowledge of​ statistics, you answer​ "it depends" and request the standard deviation of the underlying data. ​(a) Suppose the data come from a sample whose standard deviation is 3 inches. How many standard deviations is 25 inches from 16 ​inches? ​(b) Is 25 inches far away from a mean of 16 ​inches? ​(c) Suppose the standard deviation of the underlying data is 7 inches. Is 25 inches far away from a mean of 16 ​inches?

2 Answers

1 vote

Final answer:

If a measurement of 25 inches is far from a mean of 16 inches depends on the standard deviation. With a standard deviation of 3 inches, 25 inches is 3 standard deviations away, which is considered far. With a standard deviation of 7 inches, it is about 1.29 standard deviations away, which is less extreme.

Step-by-step explanation:

When determining if a measure of 25 inches is "far away" from a mean of 16 inches, it depends on the standard deviation of the underlying data.

(a) If the standard deviation is 3 inches, you calculate how many standard deviations 25 is from 16 by subtracting the mean from the measure and then dividing by the standard deviation: (25 - 16) / 3 = 9 / 3 = 3 standard deviations.

(b) With a standard deviation of 3 inches, 25 inches is indeed far away from a mean of 16 inches, as it is 3 standard deviations from the mean.

(c) If the standard deviation were 7 inches, then (25 - 16) / 7 = 9 / 7 = approximately 1.29 standard deviations. In this case, being approximately 1.29 standard deviations from the mean suggests that 25 inches is not as far from the mean as in the case with a smaller standard deviation.

The number of standard deviations away from the mean is a key factor in determining how unusual or extreme a data point is in relation to the overall data set. This is often referred to as a z-score in statistics.

User Huy
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3 votes

Answer:

a) 25 is 3 standard deviation from the mean

b) Is far away from the mean, only 0,3 % away from the right tail

c) 25 is pretty close to the mean (just a little farther from 1 standard deviation)

Step-by-step explanation:

We have a Normal Distribution with mean 16 in.

Case a) we also have a standard deviation of 3 inches

3* 3 = 9

16 (the mean) plus 3*σ equal 25 in. the evaluated value, then the value is 3 standard deviation from the mean

Case b) 25 is in the range of 99,7 % of all value, we can say that value is far away from the mean, considering that is only 0,3 % away from the right tail

Case c) If the standard deviation is 7 then

mean + 1*σ = 16 + 7 =23

25> 23

25 is pretty close to the mean only something more than 1 standard deviation

User Jnortey
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