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Same year bi n ii..... HELP!!! n also Jiyad Ahsan if u arent busyand Jiyad Ahsan
basically it says its within 12 from mean right? So that basically means its mean+12 and mean-12 which are 8 and 32.So P(8<X<32)=.94...P(8-20/r<Z<32-20/r)=.94....P(-12/r<Z<12/r)=.94 so if you remember that P(-a<z<b)=P(Z<b)+P(z<a)-1 apply that here so it becomes 2.P(Z<12/r)-1=.94 so P(Z<12/r)=(.94+1)/2....P(Z<12/r)=.97 find at what point prob is .97....so you get 12/r=1.881 ....therefore r=12/1.881=6.38
and abt the normal think that you asked i am not sure abt the np and nq>5 thing but i think you are right because in a theory ans they said you cant use normal since np<5 so i am guessing you are right i havent done all the papers but from what i saw the easiest way to do is use binomial when its small or they ask you too use normal approximation when its will take too long to do the binomial like its 200+ items or something or when they ask you to i am not sure whether i am entirely right but i think thats it