How to calculate Z-scores (formula review) (article) | Khan Academy (2024)

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• 😊

  8 years agoPosted 8 years ago. Direct link to 😊's post “how do I calculate the pr...”

  how do I calculate the probability of a z-score?

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  (20 votes)

  • Piquan

    8 years agoPosted 8 years ago. Direct link to Piquan's post “That's a great question! ...”

    

    

    That's a great question! Fortunately, the next set of lessons, at https://www.khanacademy.org/math/statistics-probability/modeling-distributions-of-data/normal-distributions-library/v/ck12-org-normal-distribution-problems-qualitative-sense-of-normal-distributions , discuss exactly that. It's great that you're thinking ahead!

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    (27 votes)
• Nick Leshuk

  8 years agoPosted 8 years ago. Direct link to Nick Leshuk's post “how do you calculate the ...”

  how do you calculate the mean when you are only given the z-scores?

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  (5 votes)

  • RacheLee

    8 years agoPosted 8 years ago. Direct link to RacheLee's post “To calculate the mean, yo...”

    

    See Also

    Standard Normal Distribution Table - Stats SolverNormal Distribution | Gaussian Distribution | Bell Curve | Normal Curve - Z TABLE

    To calculate the mean, you need to know z-scores, the data, and the standard deviation.
    z-score=(data-mean)/standard deviation
    data-mean=(z-score)(standard deviation)
    mean=(data)-(z-score)(standard deviation)

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    (14 votes)
• Tou

  6 years agoPosted 6 years ago. Direct link to Tou's post “how do you calculate this...”

  how do you calculate this: µ=10 and σ =1, P(X>10)

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  (6 votes)
• Shaghayegh

  4 years agoPosted 4 years ago. Direct link to Shaghayegh's post “Is it necessary to assume...”

  Is it necessary to assume the distribution is normal?

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  (3 votes)

  • loumast17

    4 years agoPosted 4 years ago. Direct link to loumast17's post “to use z scores. If not,...”

    to use z scores. If not, or you do not know the population standard deviation you would use a different kind of score called the t score

    For z scoreyou need both the population standard deviation and for the sample to be greater than 30.

    There are other aspects in statistics where having a normal distribution is necessary.

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    (7 votes)
• 1315031658

  7 years agoPosted 7 years ago. Direct link to 1315031658's post “How do you find the data ...”

  How do you find the data when you have the mean, the z-score, and the standard deviation?

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  (2 votes)

  • Ian Pulizzotto

    7 years agoPosted 7 years ago. Direct link to Ian Pulizzotto's post “Let x represent the data ...”

    Let x represent the data value, mu represent the mean, sigma represent the standard deviation, and z represent the z-score.
    Since the z-score is the number of standard deviations above the mean, z = (x - mu)/sigma.
    Solving for the data value, x, gives the formula x = z*sigma + mu.

    So the data value equals the z-score times the standard deviation, plus the mean.

    Have a blessed, wonderful day!

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    (7 votes)
• sebastian grez

  8 years agoPosted 8 years ago. Direct link to sebastian grez's post “what happens when you get...”

  what happens when you get the number of X-U/standar desviation ahd you get a number above 3, that number will not be in the tabla of Z

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  (4 votes)

  • psthmn

    8 years agoPosted 8 years ago. Direct link to psthmn's post “You could try to find a m...”

    You could try to find a more extensive Z table, for example here: http://www.intmath.com/counting-probability/z-table.php

    But at a certain point the difference in probality at changing z values gets vanishingly small, so it doesn't really matter what the actual value at that point is. If you are faced with this situation, in most cases P > P(Z=3) is a useful and sufficient answer.

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    (1 vote)
• Bryan

  4 years agoPosted 4 years ago. Direct link to Bryan's post “Are z-scores only applica...”

  Are z-scores only applicable for normal distributions? You could describe how many standard deviations far a data point is from the mean for any distribution right? But is the term z-score only for normal dists?

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  (3 votes)

  • Rebecca

    4 years agoPosted 4 years ago. Direct link to Rebecca's post “The z-score could be appl...”

    The z-score could be applied to any standard distribution or data set. It definition only depends on the (arithmetic) mean and standard deviation, and no other qualitative properties of the nature of the data set.

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    (2 votes)
• Samael Pena

  5 years agoPosted 5 years ago. Direct link to Samael Pena's post “What if I don't have the ...”

  What if I don't have the score but only the Z score. How can I calculate what the score is

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  (3 votes)
• muhammad fajar rizqi

  7 years agoPosted 7 years ago. Direct link to muhammad fajar rizqi's post “Hello Everybody, I want t...”

  Hello Everybody, I want to ask, how to calculate that has z-score is more than 3 or -3? because sometimes i calculate the z-score and can't get the result because it's out of range from the z-table. Thank you

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  (3 votes)
• Rosivette Andrade

  5 years agoPosted 5 years ago. Direct link to Rosivette Andrade's post “Would anyone mind explain...”

  Would anyone mind explaining this ?
  For a normal distribution of 1000 cases, how many cases will be farther away from the mean than + 3 standard deviations?

  A. about 2
  B. at least 500
  C. it is impossible to estimate
  D. 327

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  (2 votes)