**Students struggled with…**

- Determining whether to use a binomial or geometric distribution to solve a problem.
- The calculator commands for binomcdf and geometcdf for “greater than” problems.

**Remedies…**

- Encourage students to think through how they would solve the problem
**without a formula!!!!** Students get so stuck on formulas that they sometimes don’t think about a much simpler way to solve a problem. Using the general multiplication rule can be much more simple than using a geometric distribution.
- Have students write out the values that are possible for the problem. For example, if we are interested in 5 or more successes in 7 trials, write 0 1 2 3 4 5 6 7 successes. Then have students circle the values they want. Since we want 5 or more, you would circle 5 6 7. So you have to ask your calculator for 4 or less since binomcdf(
*n, p, x*) is inclusive. Students often incorrectly use 5 as the *x*-value in this scenario. By writing out the values, it’s easier for students to decide what value they need to use for a cdf function.

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