Suppose that we have a data set with a mean (µ) of 5 and a standard deviation (σ) of 4.Using the empirical rule, estimate how likely it is that a sample statistic picked at random will fall between -3 and 1.Group of answer choices68%16%13.5%50%
Question
Suppose that we have a data set with a mean (µ) of 5 and a standard deviation (σ) of 4.Using the empirical rule, estimate how likely it is that a sample statistic picked at random will fall between -3 and 1.Group of answer choices68%16%13.5%50%
Solution
To answer this question, we need to use the empirical rule, which states that for a normal distribution:
- About 68% of the data falls within one standard deviation (σ) of the mean (µ).
- About 95% of the data falls within two standard deviations (σ) of the mean (µ).
- About 99.7% of the data falls within three standard deviations (σ) of the mean (µ).
Given:
- Mean (µ) = 5
- Standard deviation (σ) = 4
We need to find the probability that a sample statistic falls between -3 and 1.
First, we calculate how many standard deviations away from the mean these values are:
-
For -3:
-
For 1:
So, -3 is 2 standard deviations below the mean, and 1 is 1 standard deviation below the mean.
According to the empirical rule:
- About 68% of the data falls within ±1σ of the mean.
- About 95% of the data falls within ±2σ of the mean.
The range from -3 to 1 is from -2σ to -1σ. This is the lower half of the range from -2σ to +2σ, which is 95%. Since the empirical rule is symmetric, the range from -2σ to -1σ is half of the range from -2σ to +2σ.
Therefore, the probability that a sample statistic falls between -3 and 1 is:
However, this is not one of the given choices. The closest match is 16%, which represents the probability of falling between -2σ and -1σ in one tail of the distribution.
Thus, the correct answer is: 16%
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