A hundred draws will be made at random with replacement from one of the followin

Question

A hundred draws will be made at random with replacement from one of the following urns, each of which contain two numbered balls. Urn A contains a 1 and a 9. Urn B contains a 4 and a 6. The value of each draw will be recorded and the mean of the 100 draws calculated. Someone offers you a dollar if you can predict the value of the sample mean to within 0.1. Which urn offers you the best chance of winning the dollar? According to the Massachusetts Department of Health, 224 women who gave birth in the state of Massachusetts in 1988 were HTV positive. At the time, a child born to an HIV positive woman had about a 25% chance of also being HIV positive. Fill in the blanks: the number of HIV positive babies born in Massachusetts in 1988 was around, give or take or so (i.e. mean plusminus standard deviation).

Explanation / Answer

1)urn B will give us best chance of winning as its values are closer and hence contains less variability in mean

2)mean =np=224*0.25=56

std deviation =(np(1-p))1/2 =6.4807

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