91Ó°ÊÓ

z-score is the number of standard deviations from the mean value a data point is.

$z-$score is the number of standard deviations from the mean value a data point is. If a z-score is equivalent to zero, the corresponding score is the mean value. If the z-score is equal to +$1$, it is one standard deviation above the mean value and if the z-score is equal to -$1$, it is one standard deviation below the mean value.

By using the z-score it can be measured by how many standard deviations ($\mathrm{σ}$), the value of x will lie below (left) or above (right) the mean ($\mathrm{μ}$) of the distribution. If the score is down the mean value, its corresponding Z score will be negative and if the score is above (right) the mean value, its corresponding z score will be positive

It is shown that the score, x=$9$is $1.5$standard deviations to the left of the mean.