Posted by **Anonymous** on Monday, September 17, 2012 at 10:34pm.

A group of 20 preschoolers were tested on reading readiness. The mean on this test is 30.9, with SD=2.08. What percentage of children scored between 25 and 28.5?

- Statistics -
**MathGuru**, Tuesday, September 18, 2012 at 4:59pm
Use z-scores.

Find two z-scores using this formula:

z = (x - mean)/sd

Mean = 30.9

Sd = 2.08

Use 25 for x to determine first z-score.

Use 28.5 for x to determine second z-score.

Once you have both z-scores, check a z-table for the probability between the two scores. Convert to a percent.

I hope this will help get you started.

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