Use the standard normal distribution table to find the z score

Z-Scores allow you to compare your data easily to other metrics.īeyond telling you just how far a particular value is from the mean, Z-scores come in handy when drawing comparisons between related but distinct metrics.įor example, imagine you are a college admissions officer reviewing an application. Note that a Z-score of zero shows that your value is equal to the mean.ģ. How far above the average? 2 standard deviations. If I tell you that an SAT score has a Z-score of 2, you know the score is above average. How far below average? 0.8 standard deviations. If I tell you your income has a Z-score of -0.8, you immediately know that your income is below average. If you need a refresher, you can visit this guide on standard deviation.Ī positive Z-score shows that your value lies above the mean, while a negative Z-score shows that your value lies below the mean. This is because most data points lie within 3 standard deviations of the mean. Typically, you will not see Z-scores that are more than 3 standard deviations from the mean. The further away your Z-score is from zero, the further away your value is from the mean. The closer your Z-score is to zero, the closer your value is to the mean. A Z-score of 2.5 means your observed value is 2.5 standard deviations from the mean and so on. Z-scores are measured in standard deviation units.įor example, a Z-score of 1.2 shows that your observed value is 1.2 standard deviations from the mean. Let’s check out three ways to look at z-scores.ġ. We can answer all of these questions in a compelling way using Z-scores.Ī Z-score is a standardized number that tells you how far away a given data point is from the mean.

Your niece was just born weighing 6.9 pounds. Is this salary high? Low? How does it compare to the incomes of other recent college graduates? You get offered a job out of college at a salary of $42,000 a year. How does Squid Game’s viewership compare to other popular series? The Netflix series Squid Game drew 111 million views in its first month on the streaming service. Life is full of instances where we want to compare an observed value against the norm. Why Z-scores Are so Important: Z-scores and Probabilities

Use the standard normal distribution table to find the z score