Review Percentiles and z scores

Front

What is a z-score?

Back

A z-score indicates how many standard deviations an element is from the mean. It is calculated as: z = (X - μ) / σ, where X is the value, μ is the mean, and σ is the standard deviation.

Front

How do you calculate a z-score?

Back

To calculate a z-score, use the formula: z = (X - μ) / σ, where X is the score, μ is the mean of the dataset, and σ is the standard deviation.

Front

What does a positive z-score indicate?

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A positive z-score indicates that the score is above the mean.

Front

What does a negative z-score indicate?

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A negative z-score indicates that the score is below the mean.

Front

If a test has a mean of 100 and a standard deviation of 15, what is the z-score for a score of 115?

Back

z = (115 - 100) / 15 = 1.00.

Front

What is the formula for finding a value from a z-score?

Back

To find a value from a z-score, use the formula: X = μ + z * σ.

Front

What is a percentile?

Back

A percentile is a measure used to indicate the value below which a given percentage of observations fall.

Front

If a student is in the 90th percentile, what does that mean?

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It means the student scored better than 90% of the other students.

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How do you find the percentile rank of a score?

Back

To find the percentile rank, use the formula: Percentile Rank = (Number of values below X / Total number of values) * 100.

Front

What is the 50th percentile also known as?

Back

The 50th percentile is also known as the median.