That said, improving the opportunities and diagnostics likely improve the metric values, so there is an indirect relationship.īelow, we've outlined why the score can fluctuate, how it's comprised, and how Lighthouse scores each individual metric. \In general, only metrics contribute to your Lighthouse Performance score, not the results of Opportunities or Diagnostics. When calculating the z-score of a sample with known population standard deviation the formula to calculate the z-score is the difference of the sample mean minus the population mean, divided by the Standard Error of the Mean for a Population which is the population standard deviation divided by the square root of the sample size.
Sample mean, sample size, population mean and population standard deviation.A raw data point, population mean and population standard deviation.This calculator can find the z-score given: You can also determine the percentage of the population that lies above or below any z-score using a z-score table.
A negative z-score means it's lower than average. The z-score allows you to compare data from different samples because z-scores are in terms of standard deviations.Ī positive z-score means the data value is higher than average. When you calculate a z-score you are converting a raw data value to a standardized score on a standardized normal distribution. You can calculate a z-score for any raw data value on a normal distribution.
The z-score is the number of standard deviations a data point is from the population mean.
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