Solve Probability on HP50g: 3 Defectives in 7 Batteries Lot

[silverbabe]

how do I use the 50g to solve this one ?

in a 80 battery lot there are 13 defectives; then, if it is taken a sample of 7 batteries. Which is the probability to find exactly 3 defectives batteries?

 

[HallsofIvy]

You don't use a calculator to solve a problem. You use a calculator to do the calculations after you have determined a strategy. What do you know about the "binomial distribution"?

 

[silverbabe]

...a strategy ?

 

[HallsofIvy]

You can use calculators to evaluate formulas, some even have formulas built in, by YOU have to know which formula to use! Again, what do you know about the "binomial distribution"?

 

[silverbabe]

I only know this one P(X=Y) (n,p,x)

 

[HallsofIvy]

Good, do you know what that means?