Z-Score

What is a z-score?

We use a z-score to calculate the size of a move of a company's share price relative to its average movement.

A very high number would show that the stock has jumped (or fallen) a great deal versus its average daily range, which is why we’ve highlighted it. It may be inconsequential, but it is outside of what we consider a normal move, so might be worth investigating.

For those interested in the maths; it is a relative excess difference from the mean, over the last 60 days worth of daily observations:

z−score  =  Latest  Price  Change  −  Mean  Price  ChangeStandard  Deviation  of  Price  Changesz-score\;=\;\frac {Latest\;Price\;Change\;-\;Mean\;Price\;Change} {Standard\;Deviation\;of\;Price\;Changes}
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What you need to know:
  • A z-score is a measure of the size of a variable relative to the variable's mean and standard deviation.
  • Z-scores can be used to determine if a value is significantly outside of a normal range.