Assuming it is a normal distribution, your z score would be. The test has a mean (μ) of 140 and a standard deviation (σ) of 30. Let's take an example and understand this better. Where x̄ is the sample means is the sample standard deviation. How to Calculate Z-score?įor a sample, the basic z- score formula is When you 'standardize' a variable, its mean becomes zero and its standard deviation becomes one. Z-scores range from -3 standard deviations up to +3 standards.Ī Z-score can help us in determining the difference or the distance between a value and the mean value.
A raw score as a Z-score can also be called a standard score and it can be placed on a normal distribution curve. A data point is a measure of how many standard deviations are below or above the mean. Z-score can be defined as the number of standard deviations from the mean.
