Mr. and Mrs. Doran have a genetic history such that the probability that a child
being born to them with a certain trait is 87%. If they have seven children,
what is the probability that at least four of their seven children will have
that trait? Round your answer to the nearest thousandth.
There are two ways to do it with a TI-83 or 84
FIRST WAY:
The complement event is that 3 or fewer will have that trait.
Press 2ND VARS and scroll down to binomcdf(, [careful, not binompdf(]
that's 7 trials, p=0.87, x value 3
Should have on your screen
binomcdf(7,0.87,3)
press ENTER
0.0072028157
Subtract from 1.
1-0.0072028157
0.9927971843 round to 0.993
--------------------------------
SECOND WAY
That's the same thing as 3 or fewer will not have the trait.
The probability of not having the trait is 1-0.87=0.13.
Press 2ND VARS and scroll down to binomcdf(, [careful, not binompdf(]
that's 7 trials, p=0.13, x value 3
Should have on your screen
binomcdf(7,0.13,3)
press ENTER
0.9927971843 round to 0.993
Edwin