2.12 School absences. Data collected at elementary schools in DeKalb County, GA
ID: 3306121 • Letter: 2
Question
2.12 School absences. Data collected at elementary schools in DeKalb County, GA suggest that each year roughly 25% of students miss exactly one day of school, 15% miss 2 days, and 28% miss 3 or more days due to sickness. 61 (a) What is the probability that a student chosen at random doesn't miss any days of school due to sickness this year? (b) What is the probability that a student chosen at random misses no more than one day? (c) What is the probability that a student chosen at random misses at least one day? (d) If a parent has two kids at a DeKalb County elementary school, what is the probability that neither kid will miss any school? Note any assumption you must make to answer this question. (e) If a parent has two kids at a DeKalb County elementary school, what is the probability that both kids will miss some school, ie at least one day? Note any assumption you make. (f) If you made an assumption in part (d) or (e), do you think it was reasonable? If you didn't make any assumptions, double check your earlier answers.Explanation / Answer
a) probability does not miss =1-0.25-0.15-0.28=0.32
b)probability =P(X<=1)=P(X=0)+P(X=1) =0.32+0.25=0.57
c) P(X>=1) =1-P(X=0)=1-0.32=0.68
d)probability that neither kid miss any school =0.32*0.32=0.1024 (considering both events independent)
e)probabilty that both kids miss some school =(1-0.32)*(1-0.32)=0.4624
f)we have assumed that going to school probability for both kids is independent of each other, That does not seem much reasonable as being kids of same parent their school going tendency should be positivily correlated
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