annna's problems with probability/binomial distribution thread

[physics]

Rex is shooting at a target. His probability of hitting the target is 0.6. What is the minumum number of shots needed for the probability of Rex hitting the target exactly 5 times to be more than 25%?

ANS: 7

Janet is selecting chocolates at random out of a box. She knows that 20% of the chocolates  have hard centres. What is the minimum number of chocolates she needs to select to ensure that the probability of choosing exactly 3 hard centres is more than 10%?

ANS: 7

Monique is practising goaling for netball. SHe knows from past experience that her chances of maing any one shot is about 70%. Her coach has asked her to keep practising until she scores 50 goals. How many shots would she need to attempt to ensure that the probability of making at least 50 shots is more than 0.99?


ANS: 86


Please show the working out to how you got these answers.   thankss

[JuzzLee]

Monique is practising goaling for netball. SHe knows from past experience that her chances of maing any one shot is about 70%. Her coach has asked her to keep practising until she scores 50 goals. How many shots would she need to attempt to ensure that the probability of making at least 50 shots is more than 0.99?

trial n error if non-cas, doesn't take long. the x-value is too large, otherwise method on p492 can work. if you do cas, then everything is cool

[physics]

Monique is practising goaling for netball. SHe knows from past experience that her chances of maing any one shot is about 70%. Her coach has asked her to keep practising until she scores 50 goals. How many shots would she need to attempt to ensure that the probability of making at least 50 shots is more than 0.99?

trial n error if non-cas, doesn't take long. the x-value is too large, otherwise method on p492 can work. if you do cas, then everything is cool

i'm really confused about that question casue u can't sue the smae method as you did for the other questions in that exercise

[/0]

Do you have TI-89? TT outlined a method of solving it somewhere, but in short, you have to put binomCdf() in your y-editor. Since the function works like "binomCdf(number of trials, probability of success, lower bound, upper bound)",

Input into your Y= editor:

Code: [Select]

binomcdf(x,0.7,50,x)Since you are summing the probabilities of: making 50 shots in 50 attempts, 50 shots in 51 attempts, 50 shots in 52 attempts... 50 shots in x attempts.

This is a discrete function, so you can't view it on a graph. Instead you must use a table. Go diamond+F4 to set your table specifications, then go to diamond+F5 to view your table. Scroll down until the probability is greater than 0.99 and that will be your value for x.

[khalil]

DOES ANYONE KNOE HOW TO DO IT ON THE TI-Nspire?
My teacher has no clue.
Im so desperate I even emailed the auther of essentials

[timivett]

DOES ANYONE KNOE HOW TO DO IT ON THE TI-Nspire?
My teacher has no clue.
I'm so desperate I even emailed the author of essentials

There's probably an easier way to do it on a TI-Nspire but this will work:
1. Go to Add Lists & Spreadsheets
2. In column A, list the numbers between the lower bound and upper bound for the number of trials (for lower bound use 50, then estimate an upper bound.. eg. 100). You can type 50 and then 51 then highlight these two and fill down to 100 by pressing menu, data, fill, press down key until about cell 50.
3. In cell B1 (or to the right of where you listed your lower bound), enter the formula =binomcdf(a1,0.7,50,100)
which is binomcdf(number of trials, probability of success, upper bound, lower bound).
4. Fill this formula all the way down to where you have your upper bound number (100) in the A column.
5. Scroll down the table until the number in the B column (the probability) is greater than 0.99... which should be 86.