Why n-1 and not n?
By Vasant Marur
Discussion
A brief discussion of standard deviation concepts.
Descriptives
These are the descriptive statistics of the complete data set with 398 values
Descriptive Statistics
|
N |
Range |
Minimum |
Maximum |
Mean |
Std. Deviation |
Variance |
Skewness |
|---|
| Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Std. Error |
|---|
| Miles per Gallon |
398 |
38 |
9 |
47 |
23.51 |
7.816 |
61.090 |
.457 |
.122 |
|---|
| Valid N (listwise) |
398 |
|
|
|
|
|
|
|
|
|---|
Graph
Histogram with Normal Curve of Miles per gallon of the complete data set with 398 values
Graph
Histogram with Normal Curve of Miles per gallon.
These are 125 randomly sampled values,about 35% of the complete data set
Descriptives
Descriptive Statistics of Miles per gallon.
These are 125 randomly sampled values,about 35% of the complete data set
Descriptive Statistics
|
N |
Range |
Minimum |
Maximum |
Mean |
Std. Deviation |
Variance |
Skewness |
|---|
| Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Statistic |
Std. Error |
|---|
| Miles per Gallon |
125 |
30 |
13 |
43 |
23.12 |
7.668 |
58.796 |
.589 |
.217 |
|---|
| Valid N (listwise) |
125 |
|
|
|
|
|
|
|
|
|---|
Notice the Red Highlighted Table Cell, You will notice that the Standard Deviation of the sample is
approximately equal to the Standard Deviation of the Population above
It is approximately equal as it is an estimator of the Standard Deviation of the Population