Respuesta :
From the given data, mean, and deviations from the mean, the
completed statement is presented as follows;
If this is sample data, the sample variance is 16.268 and the sample
standard deviation is 4.033. If this is population data, the population
variance is 14.234, and the population standard deviation is 3.773.
Suppose the smallest value of 84 in the data was misrecorded as 85, if
you were to recalculate the variance and standard deviation with 85
instead of the 84, your new values for the variance and standard
deviation would be; for the sample, 14.875, 3.857, for the population,
13.016, 3.608, respectively.
How can the variance and the standard deviation be found?
The definitional formula for the variance is presented as follows;
[tex]Sample \ variance, \, s^2 = \mathbf{\dfrac{\sum \left(x - \overline x \right)^2}{N - 1}}[/tex]
[tex]Population \ variance, \, \sigma^2 =\mathbf{\dfrac{\sum \left(x - \overline x \right)^2}{N }}[/tex]
Where;
s = The standard deviation of the sample
σ = The standard deviation of the population
N = The sample size
From the given deviations from the mean, (x - [tex]\overline x[/tex])², we have;
∑(x - [tex]\overline x[/tex])² = (2.625)² + (-5.375)² + (-4.375)² + (3.625)² + (5.625)² + (-0.375)² + (-3.375)² + (1.625)² = 113.875
[tex]s^2 = \dfrac{113.875}{8 - 1} \approx \mathbf{16.268}[/tex]
- The sample variance is approximately 16.268
- The sample standard deviation is therefore; s ≈ √(16.268) ≈ 4.033
The population variance, σ², is found as follows;
[tex]\sigma ^2 = \dfrac{113.875}{8 } \approx \mathbf{14.234}[/tex]
- The population variance is approximately 14.234
- The population standard deviation is, σ = √(14.234) ≈ 3.773
Given that 84 is replaced with 85, we have;
The lowest deviation from the mean, -5.375, will be -4.375, which gives;
∑(x - [tex]\overline x[/tex])² = (2.625)² + (-4.375)² + (-4.375)² + (3.625)² + (5.625)² + (-0.375)² + (-3.375)² + (1.625)² = 104.125
The new values are as follows;
- [tex]\mathbf{s_{new}^2} = \dfrac{104.125}{8 - 1} \approx \underline{14.875}[/tex]
- [tex]\mathbf{s_{new}}= \sqrt{14.875} \approx \underline{3.857}\alpha[/tex]
- [tex]\mathbf{\sigma_{new}^2} = \dfrac{104.125}{8 } \approx \underline{ 13.016}[/tex]
- [tex]\mathbf{\sigma_{new}} = \sqrt{13.016} \approx \underline{3.608}[/tex]
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