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## AP®︎/College Statistics

### Course: AP®︎/College Statistics>Unit 14

Lesson 1: Prepare for the exam

# Significance test for a proportion free response example

Carrying out every step of a significance test on a proportion.

## Want to join the conversation?

• Why do we assume the significance level is 0.05? (timestamp )
• That's just a typical significance level. We could have chosen 0.01 or 0.1 as well, which are also typical significance levels, but it's worth noting that with any of these, we still get the same result (failing to reject the null hypothesis) in the original problem.
• Hi, why the standard deviation that you plug in the calculator is 1, instead of 0.0496?
• This is to ensure that the upper bound is equal to the z-score. The normalcdf function does not take in z-scores; it finds the area between a concrete lower and upper bound (rather than a relative z-score) given a mean and standard deviation. So, in order to make the bounds equal to the z-scores, the standard deviation is set to 1.
• when do you put the upper/lower bounds as infinity and negative infinity as opposed to 1 and 0? if it's a proportion wouldn't the distribution only go from 0 to 1? or are you assuming it has infinitely long tails to make it a true normal distribution?
• How did you get 0.8 ?
• How much time are you given for this problem? Is this one of the longer free response, or the shorter ones?
(1 vote)
• hi wus up man:)
(1 vote)
• How much time are you given for this problem? Is this one of the longer free response, or the shorter ones?
(1 vote)
• If you divide up your time, you should have about 15 minutes for each question.
(1 vote)
• Could we have used a binomial distribution instead of a normal distribution and if so would the probability of getting less than or equal to 11 be binomCdf(n=65, p=.2, Lower Bound: 0, Upper Bound 11) which gives .33 much different from Sal's .266
(1 vote)
• I still don't understand it and why do we have to do more than you on the video and you are good at math. I also need a tutor.
(1 vote)