A z-score, also called a standard score, gives you an idea of how far from the mean a data point is. But more technically it\u2019s a measure of how many standard deviations below or above the population mean a raw score is.
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A z-score can be placed on a normal distribution curve. Z-scores range from -3 standard deviations (which would fall to the far left of the normal distribution curve) up to +3 standard deviations (which would fall to the far right of the normal distribution curve). In order to use a z-score, you need to know the mean \u03bc and also the population standard deviation \u03c3.<\/p>\n
z = (x \u2013 \u03bc) \/ \u03c3<\/strong><\/p>\n Z-scores are a way to compare results to a \u201cnormal\u201d population. This is quickly analyze outliers or can be used to clean datasets and prevent bias from outliers. You can clip the outliers to the max and min of the +3 and -3 standard deviations. This is very useful when datasets get very large.<\/p>\n to get the mean \u03bc use =Average()<\/p>\n to get the standard deviation \u03c3 use =STDEV()<\/p>\n Z-scores you can use =STANDARDIZE(range, mean, standard deviation)<\/p>\nExcel offers the following formulas to help:<\/h2>\n