3. -0.6 points My Notes Visual sequential memory and poor spellers. Holmes, Malo

Question

3. -0.6 points My Notes Visual sequential memory and poor spellers. Holmes, Malone, and Redenbach (2008) found that good readers and good spellers correctly read M·93.8 (SD 2.9) words from a spelling list. On the other hand, average readers and poor spellers correctly read M-84.4 (SD 3.0) words from the same spelling list. Assuming these data are normally distributed, (use 2 decimal places) (a) What percentage of participants correctly read at least 90 words in the good readers/good spellers group? (b) What percentage of participants correctly read at least 90 words in the average readers/poor spellers group?

Explanation / Answer

a) Since =93.8 and =2.9 we have:

P ( X>90 )=P ( X>9093.8 )=P ( (X)/>(9093.8)/2.9)

Since Z=(x)/ and (9093.8)/2.9=1.31 we have:

P ( X>90 )=P ( Z>1.31 )

Use the standard normal table to conclude that:

P (Z>1.31)=0.9049= 90= 90%

b) Since =84.4 and =3.0 we have:

P ( X>90 )=P ( X>9084.4 )=P ((X)/>(9084.4)/3.0)

Since Z=(x)/ and (9084.4)/3.0=1.87 we have:

P ( X>90 )=P ( Z>1.87 )

Use the standard normal table to conclude that:

P (Z>1.87)=0.0307= 0.03= 3%

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