AP Exam Review #1

A flour company in Indianapolis wants to know what percent of local households bake at least twice a week. A company representative calls 500 randomly-selected households during the daytime and finds that 72% of those who responded bake at least twice a week. Which type of bias is most likely present?

Let X be a random variable that has a skewed distribution with mean 10 and standard deviation 10. Based on random samples of size 400, the sampling distribution of X will be

• skewed with mean 10 and st. dev. 10

• skewed with mean 10 and st. dev. 0.5

• normal with mean 10 and st. dev. 10

• normal with mean 10 and st. dev. 0.5

A factory runs 24 hours a day, producing 15,000 wood pencils per day over three 8-hour shifts - day, evening, and overnight. In the last stage of manufacturing, the pencils are packaged in boxes of 10 each. Each day a sample of 300 pencils is selected and inspected for quality. The quality control supervisor recommends numbering the boxes from 1 - 1500 and using a calculator to select 30 boxes to check. This is an example of a (n) _________ sample.

• convenience

• simple random

• stratified

• cluster

Companies are interested in the demographics of those who listen to the radio programs they sponsor. A radio station has determined that only 20% of listeners phoning in to a morning talk program are male. The station manager wonders if adding a male host to the program will increase the proportion of callers who are male. After adding the male host, the station records 100 people who phone in to the program during a particular week. The station is willing to view these 100 callers as an SRS from the population of those who call in to this program. Suppose the manager wants to make the spread half of what it currently is. What should you tell the manager the sample size should be to accomplish this?

A local university has a “drop-in center” located near the Student Union where students can “drop-in” to speak to a counselor on any issue or concern whether personal or academic. A researcher stations herself at a receptionist’s desk during a few random evenings to collect data and see whether men or women are more likely to use this service and whether a particular class (freshman, sophomore, junior, senior) is more likely to “drop-in.” This may be described as...

• a controlled experiment

• a matched pairs design experiment

• an observational study

• a double blind completely randomized experiment

A study of college freshmen’s study habits found that the time (in hours) that freshmen use to study each week follows a distribution with a mean of 7.2 hours and a standard deviation of 5.3 hours. Find the probability that the average number of hours spent studying by an SRS of 50 students is greater than 9 hours. Round any step to the nearest hundredth, including your answer.

A popcorn lover wants to determine if it is better to use the “popcorn button” on her microwave over or use the amount of time recommended on the bag of popcorn.  To measure how well each method works, she will count the number of unpopped kernels remaining after popping.  To obtain the experimental units, she goes to the store and buys 10 bags each of 4 different varieties of microwave popcorn (butter, cheese, natural, and kettle corn), for a total of 40 bags.  Which option below would be the ideal way to block this experiment?

• blocking by variety of popcorn

• blocking on popping time

• blocking on microwave manufacturer

• without blocking

Companies are interested in the demographics of those who listen to the radio programs they sponsor.  A radio station has determined that only 20% of listeners phoning in to a morning talk program are male.  The station manager wonders if adding a male host to the program will increase the proportion of callers who are male.  After adding the male host, the station records the number of 100 people who phone in to the program during a particular week.  The station is willing to view these 100 callers as an SRS from the population of all those who call in to this program. Should we be suspicious of getting a sample of 30 males from the SRS of 100?

• Yes, suspicious because the probability is less than 5%.

• Yes, suspicious because the probability is more than 5%

• No, not suspicious because the probability is less than 5%

• No, not suspicious because the probability is more than 5%

Another AP Stats teacher tries to replicate our vocabulary and music experiment.  He takes a SRS of 100 students from his small, rural high school and randomly assigns them to two groups.  One group studies while listening to classical piano music, and the other group studies while listening to Drake.  Based on how he set up this experiment, which of the following conclusions can he draw?

• He can generalize to the population and can draw cause and effect conclusions.

• He can generalize to the population but can not draw cause and effect conclusions.

• He can't generalize to the population but can draw cause and effect conclusions.

• He can't draw any conclusions.