The accompanying data on x = head circumference z score (a comparison score with

Question

The accompanying data on x = head circumference z score (a comparison score with peers of the same age - a positive score suggests a larger size than for peers) at age 6 to 14 months and y = volume of cerebral grey matter (in ml) at age 2 to 5 years were read from a graph in an article.

  


(c) Predict the volume of cerebral grey matter for a child whose head circumference z score at age 12 months was 1.8. (Give the answer to two decimal places.)

Cerebral Grey
Matter (ml) 2-5 yr Head Circumfer-
ence z Scores at
6-14 Months 680 -0.71 690 1.8 700 -0.26 720 0.29 740 0.34 740 2.1 750 1.7 750 2.6 760 1.7 780 1.7 790 2.6 810 2.7 815 3.4 820 2.8 825 0.94 835 2.95 840 2.9 845 2.8

Explanation / Answer

a)

Using technology, like the CORREL function in Excel,
              
r =    0.741233625   [ANSWER]      

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b)

Using technology, we get              
              
slope =    32.80079564          
intercept =    712.7163478          
              
Thus, the regression line is              
              
y^ =    32.80079564x +   712.7163478 [ANSWER]

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c)
Thus, if x =    1.8  
      
Then      
      
y^ =    771.75778 [ANSWER]  
              

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