AP Stats Binomial Distribution

The supply manager at a local ice cream shop claims that 80% of customers prefer chocolate over vanilla. One of the employees believes that is an overstatement. He selects a random sample of 50 customers and found that 30 of them preferred chocolate over vanilla. Which of the following is the appropriate margin of error for a 95 percent confidence interval to estimate the population proportion of all customers that prefer chocolate over vanilla?

Answer explanation

The correct answer is (C). The critical value for a 95 percent confidence interval for one proportion is 1.96. The sample proportion  = 30/50 = 0.6 and the sample size n = 50. The value of 0.8 is not used in this case, because this is simply a claim that is made about the proportion of customers that prefer chocolate over vanilla. 

Suppose 39% of Americans will vote for Donald Trump on election day. If a random sample of 8 voters are selected, what is the probability that 6 or more will vote for Trump?

• .9635

• .0365

• .9561

• .0439

A survey found that 25% of pet owners had their pets bathed professionally rather than do it themselves. If 18 pet owners are randomly selected, find the probability that exactly 5 people have their pets bathed professionally

• 3.42

• 1.03

• 0.072

• 0.199

The student who makes the morning announcements has the bad habit of saying “like” all the time. The chance that they say “like” in a sentence is 60%. You decide to keep a tally of how many times they say like. If they say 350 sentences this week, what is the probability that they will say “like” at least 200 times?

• 0.87

• 0.13

• 0.85

• 0.15

True or False:

exactly = binompdf

at most = binomcdf

at least = binomcdf

• True

• False

If you were to flip a coin 20 times, what is the probability you would get at most 13 heads?

• .9423

• .1316

• .0577

• .0739

In Vietnam, the probability of rain is 70%.  Find the probability of it raining at most 2 days in a week.

• .9712

• .0250

• .0287

• .2988

In Vietnam, the probability of rain is 70%.  Find the probability of it raining at most 5 days in a week.

• .9712

• .6705

• .3294

• .5520

The American Red Cross says that about 11% of the U.S. population has Type B blood. A blood drive is being held at your school. What is the probability that at least 2 of the first 10 blood donors has Type B blood? 

• 0.088

• 0.697

• 0.214

• 0.303 

A research team at Cornell University conducted a study showing that approximately 10% of all businessmen who wear ties wear them so tightly that they actually reduce blood flow to brain, diminishing cerebral functions. At a board meeting of 20 businessmen, all of whom wear ties, what is the probability that at least one tie is too tight?

• 27.0%

• 12.2%

• 73.0%

• 87.8%