When you want to print these results, select the Print command in the Files menu, or press Ctrl+P. 

Sample size: the number of cases n is the number of numeric entries for the variable that fulfill the 

selection criterion.  

The lowest value and highest value of all observations (range). 

Arithmetic mean: the arithmetic mean 

X

 is the sum of all observations divided by the number of 

observations n: 

X

X

n

95% confidence interval (CI) for the mean: this is a range of values, calculated using the method 

described later (see Standard Error of the Mean), which contains the population mean with a 95% 

probability. 

Median: when you have n observations, and these are sorted from smaller to larger, then the median is 

equal to the value with order number (n+1)/2.  The median is equal to the 50th percentile.  If the 

distribution of the data is Normal, then the median is equal to the arithmetic mean.  The median is not 

sensitive to extreme values or outliers, and therefore it may be a better measure of central tendency than 

the arithmetic mean. 

95% confidence interval (CI) for the median: this is a range of values that contains the population 

median with a 95% probability (Campbell & Gardner, 1988).  This 95% confidence interval can only be 

calculated when the sample size is not too small. 

Variance: the variance is the mean of the square of the differences of all values with the arithmetic mean.  

The variance (s

2 

) is calculated using the formula: 

(X

X)

2

s

2

n

1

Standard deviation: the standard deviation (s or SD) is the square root of the variance, and is a measure 

of the spread of the data:  

44