ap stats chapter 9-10-11 khans(at least the ones that confused me!)

Does each digit 0-9 appear with the same frequency in π? Juan tallied how many times each digit appeared in the first 1000 digits of π. Here are the results: What is the expected count of the digit 1?

100

A media streaming website knows that 70% percent of its customers primarily watch on their television, 18%, percent primarily watch on their computer, and 12%, percent primarily watch on a mobile device. The company wonders if these percentages hold true after a recent update to the product. They take a random sample of 700 customers and obtain these results: What is the expected count of customers that watch on their computer in the sample?

126

A large restaurant chain wanted to determine if its employees were taking sick days on some days of the week more than others. They took a random sample of 140 sick days taken and recorded the day of the week for each sick day. Here are the results: What is the expected count of sick days taken on Saturday?

140/7=20

Mabel runs a website, and she wonders how people navigate to her website. She suspects that 50% percent of visitors arrive from a web search, 25%, percent arrive from links on social media, and 25%, percent arrive directly by entering the website's address. She plans to take a random sample of visitors and record how they navigated to the site in order to perform chi-squared goodness-of-fit test on the results. What is the smallest sample size Mabel can take to pass the large counts condition?

20

Jiao works as an usher at a theater. The theater has 1000 seats that are accessed through five entrances. Each guest should use the entrance that's marked on their ticket. Jiao wants to test if the distribution of guests according to entrances matches the official distribution. He collects information about the number of guests that went through each entrance at a certain night. Here are the results: What is the expected count of guests in entrance A, end text in Jiao's sample?

300

Jacqueline works as a quality control expert at a factory that packages different chocolates in variety packs. She selected a random container to see how well the 220 chocolates inside matched the advertised distribution. The table below shows the advertised distribution and the observed counts for each type of chocolate in the container she selected. What is the expected count of salted caramel chocolates in Jacqueline's sample?

44

Nina wanted to test if her 6-sided die was fair. In other words, she wanted to test if some sides get rolled more often than others. She rolled the die 60 times and recorded how often each side was rolled. Here are her results: What is the expected count of rolls to land showing a 3?

60/6=10 ANSWER IS 10

Ciara, an ornithologist, has 4 bird feeders at separate locations. She wonders if birds are equally likely to visit each of the feeders. She recorded data for a sample of 350 recent visits. Here are the results: What is the expected count of visits to the third feeder?

87.5

Preston teaches at an international school. After reading an article about the distribution of the world's population by continent, he wanted to test if the distribution of students in his school was similar. He collected information about all 320 students in his school. Here are the results: Preston wants to perform an x-squared goodness-of-fit test to determine if these results suggest that the distribution of students doesn't match the reported distribution.

EC=1.6

A sociologist studying fertility in France and Switzerland wanted to test if there was a difference in the average number of babies women in each country have. The sociologist obtained a random sample of women from each country. Here are the results of their test:

No, since the P-value is greater than .05

According to the distributor of a kind of trading card, 66% percent of the cards are common, 25% percent are uncommon, and 9% percent are rare. Pin-Yen wondered if the rarity levels of the cards she and her friends owned followed this distribution, so she took a random sample of 500 cards and recorded their rarity levels. Here are her results: What are the values of the test statistic and P-value for Pin-Yen's test?

Test stat: 5.682 .05<p-value<.10

A sociologist studying fertility in Venezuela and Colombia wanted to test if there was a difference in the average number of babies women in each country have. The sociologist obtained a random sample of women from each country. Here is a summary of their results:

The P-value is greater than a=.10 and they cannot conclude that there is a difference between the means.

Ignacio grows two varieties of apples—Honeycrisp and Gala. He took a sample of each variety to test if their mean weights were significantly different. Here is a summary of his results (weights are shown in grams):

The P-value is less than a=.10, and he should conclude that there is a difference between the means.

Felipe works at a factory that uses two independent production lines—line A and line B—to fill bottles with a beverage. He runs a daily test on separate random samples from each line to see if there is a difference in the average filling amounts (in milliliters) between the two lines. Here are results from the most recent test:

Yes, since the P-value is less than .05

Lennox had been scheduling employees based on the assumption that the following distribution represented when people made purchases in his store. He took a random sample of 300 purchases and recorded their time slot so he could test whether this was an accurate distribution. Here are his results: What are the values of the test statistic and P-value for Lennox's test?

test stat.: 10.5 .01<P-value<.02

In the following table, Meryem modeled the number of rooms she believes are in use at any given time at the veterinary hospital where she works. To test her model, she took a random sample of 80 times and recorded the numbers of rooms in use at those times. Here are her results: What are the values of the test statistic and P-value for Meryem's test?

test stat.=4 p-value>.25

In the game rock-paper-scissors, Kenny expects to win, tie, and lose with equal frequency. Kenny plays rock-paper-scissors often, but he suspected his own games were not following that pattern, so he took a random sample of 24 games and recorded their outcomes. Here are his results: What are the values of the test statistic and P-value for Kenny's test?

test statistic: 5.25 p-value: .05<p-value<.10