Use the range rule of thumb to identify the values that are significantly low, the values that are signficantly high, and the values that are neither significantly low nor significantly high.
A test is used to assess readiness for college. In a recent year, the mean test score was 21.2 and the standard deviation was 4.9 . Identify the test scores that are significantly low or significantly high.

The standard score is the number of standard deviations by which the value of a raw score is above or below the mean value of what is being observed or measured.

Here, we are dealing with z scores, then the distribution is a normal distribution. The formula for determining the z score is expressed as

z = (x - µ)/σ

Where, x = sample mean, µ = population mean σ = standard deviation

From the information given,

µ = 21.9

σ = 4.9

For significantly low values, z = - 2

Therefore,

- 2 = (x - 21.9)/4.9

- 2 × 4.9 = x - 21.9

- 9.8 = x - 21.9

x = - 9.8 + 21.9

x = 12.1

Significantly low test score = 12.1

For significantly high values, z = 2

Therefore,

2 = (x - 21.9)/4.9

2 × 4.9 = x - 21.9

9.8 = x - 21.9

x = 9.8 + 21.9

x = 31.7

Thus, the Significantly low test score is 12.1 and significantly high score value is 31.7.

Learn more about z-score from:

https://brainly.com/question/15016913

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