Mean, Variance and Standard deviation (population&sample)

Mean, Variance and Standard deviation (population&sample)

1. MEAN

   • Calculated by summing the meausrements and then dividing by the number of measurements contained in the data set
   • Formula
     • 1/N (X1+X2+X3+X4+X5)
       • 1/5 (3.5+12.3+ 17.7+20.9+23.1)=15.5

2. VARIANCE

   • A measure of how spread out the scores
   • 1/N (difference form the mean)2
   • It is not given in the units of the datat set. variance is just a measure of spread, is unit free

3. STANDARD DEVIATION

   • Squared root of variance
     • √Variance
     • EX: √49.2=7.0