ADHD? OR JUST YOUNGEST IN THE CLASS? A study1 indicates that the youngest children in a school grade are more likely to be diagnosed with attention-deficit/hyperactivity disorder (ADHD) than their older peers in the same grade. The study involved 937,943 children between 6 and 12 years old in British Columbia, Canada. The cutoff date for entering school in any year in British Columbia is December 31st, so in any given class, those born late in the year are almost a year younger than those born early in the year. Is it possible that the younger students are being over-diagnosed with ADHD? Boys: ADHD or Just Young? The table below shows the number of boys diagnosed with ADHD based on the quarter of the year in which they were born, as well as the proportion of boys born during that quarter. Birth Date ADHD Diagnoses Proportion of Births Jan-Mar 6880 0.244 Apr-Jun 7982 0.258 Jul-Sep 9161 0.257 Oct-Dec 8945 0.241 Table 1 ADHD diagnoses and birth date for boys 1Morrow, R., et al., “Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children,” Canadian Medical Association Journal, April 17, 2012; 184(7): 755–762.     (a) What is the total number of boys diagnosed with ADHD in the sample? Total number of boys = _______   (b) For the null hypothesis, use the overall proportion of births in a quarter to give the null proportion for that quarter. Compute the expected number of ADHD diagnoses for each quarter under this hypothesis. Round your answers to one decimal place. Jan-Mar  =  _________ Apr-Jun  =  _______ Jul-Sep  =  _______ Oct-Dec  =  _______   (c) Compute the χ2-statistic. Round your answer to one decimal place. χ2 = _____   (d) Give the degrees of freedom and find the p-value. Enter the exact answer for the degrees of freedom, and round your answer for the p-value to three decimal places. d⁢f= ______ p-value =______   (e) State the conclusion of the test. a- There is very strong evidence that ADHD diagnoses are related to relative age. b- ADHD diagnoses do not seem to be related to relative age in school. c- There is some evidence that ADHD diagnoses are related to relative age.

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ADHD? OR JUST YOUNGEST IN THE CLASS?

A study1 indicates that the youngest children in a school grade are more likely to be diagnosed with attention-deficit/hyperactivity disorder (ADHD) than their older peers in the same grade. The study involved 937,943 children between 6 and 12 years old in British Columbia, Canada. The cutoff date for entering school in any year in British Columbia is December 31st, so in any given class, those born late in the year are almost a year younger than those born early in the year. Is it possible that the younger students are being over-diagnosed with ADHD?

Boys: ADHD or Just Young?

The table below shows the number of boys diagnosed with ADHD based on the quarter of the year in which they were born, as well as the proportion of boys born during that quarter.

Birth Date ADHD Diagnoses Proportion of Births
Jan-Mar 6880 0.244
Apr-Jun 7982 0.258
Jul-Sep 9161 0.257
Oct-Dec 8945 0.241

Table 1 ADHD diagnoses and birth date for boys


1Morrow, R., et al., “Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children,” Canadian Medical Association Journal, April 17, 2012; 184(7): 755–762.
 
 
(a) What is the total number of boys diagnosed with ADHD in the sample?

Total number of boys = _______
 
(b) For the null hypothesis, use the overall proportion of births in a quarter to give the null proportion for that quarter. Compute the expected number of ADHD diagnoses for each quarter under this hypothesis.

Round your answers to one decimal place.

Jan-Mar  =  _________

Apr-Jun  =  _______

Jul-Sep  =  _______

Oct-Dec  =  _______
 
(c) Compute the χ2-statistic.

Round your answer to one decimal place.

χ2 = _____
 
(d) Give the degrees of freedom and find the p-value.

Enter the exact answer for the degrees of freedom, and round your answer for the p-value to three decimal places.

d⁢f= ______
p-value =______
 

(e) State the conclusion of the test.

a- There is very strong evidence that ADHD diagnoses are related to relative age.
b- ADHD diagnoses do not seem to be related to relative age in school.
c- There is some evidence that ADHD diagnoses are related to relative age.
 
(f) For which group of children does ADHD appear to be diagnosed more frequently than we would expect? Select the group that provides the greatest indication of this.

a- Jan-Mar
b- Apr-Jun
c- Jul-Sep
d- Oct-Dec
 
(g) For which group of children does ADHD appear to be diagnosed less frequently than we would expect? Select the group that provides the greatest indication of this.

a- Jan-Mar
b- Apr-Jun
c- Jul-Sep
d- Oct-Dec
 
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