Question

Monique is practicing goal shots for netball. She knows from experience that her chance of making any one shot is70%. She plans to practice until she scores 50 goals. How many shots must she attempt to ensure that the probability of making at least 50 goals is more than 0.99?

What do I need to input in the Ti nspire under:

--> probability  --> distributions --> Inverse binomial N

Ti-nspire CX Form

Cummulative Prob: ?
Prob of Success: ?
Successes, x: ?

and why these number and whats the output of this form and final result?

Answer 1

Here we want to find n such that P( X >= 50) >= 0.99

This implies that P(X <= 50-1 ) < 1 - 0.99 = 0.01

P(X <= 49 ) < 0.01

Where X follows binomial distribution with probability of success is 0.70

Therefore we need to put

cumulative probability = 0.01

Probability of success = 0.70

number of successes = x = 49.

Cumulative  Prob : 0.01

Prob of success : 0.70

Successes, x : 49

When we put these values, then we get answer as 86.