Statistics
posted by Anonymous .
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?

Use zscores.
Find two zscores using this formula:
z = (x  mean)/sd
Mean = 30.9
Sd = 2.08
Use 25 for x to determine first zscore.
Use 28.5 for x to determine second zscore.
Once you have both zscores, check a ztable for the probability between the two scores. Convert to a percent.
I hope this will help get you started.