Samples and Populations Statistics

Tom Ricketts wants to survey people who visit Wrigley Field and identify their favorite jersey the Cubs wear.  For his survey, the population is defined as all people who visit Wrigley Field in May.  The number of people in this population is large, so Tom realizes that he must choose a sample of the population to survey.  Which sample would be the best representation of the population?

• A random sample of 100 fans who visited Wrigley Field on Sundays.

• A random sample of 100 fans in the bleachers of Wrigley Field during May.

• A random sample of 100 females who visited Wrigley Field during May.

• A random sample of 100 people who visited Wrigley Field during May.

Which of the following methods would be appropriate for choosing a random sample of ten students from the 7th grade?

• Choose 10 students from your lunch table.

• Get a print out of all the students in 7^th grade and choose every 10^th student.

• Assign every student a number and use a random number generator to select 10 numbers.

• Choose the first 10 students to get to your PE class.

Students are surveyed about the average number of minutes they spend getting ready each morning.  Which sample size will most likely have the least amount of variability?

• 10

• 20

• 30

• 40

Ben conducted a random sample of 20 students from his school to find out their favorite kind of pizza.  He found that 7 of the surveyed students prefer sausage.  What percentage of the students at Ben’s school are likely to prefer sausage pizza?

• 7%

• 25%

• 35%

• 77%

Tyler picked a random sample of the students on his track team and surveyed their heights.  He found that the mean of their heights was 58 inches.  Choose the conclusion that would be most appropriate for Tyler to make.

• The mean height of all random samples would be 58 inches.

• The mean height of all students on the track team is likely to be close to 58 inches.

• The mean height of all students on the track team is exactly 58 inches.

• If  a smaller sample was chose, the mean age would be smaller than 58 inches.

The number of iTunes downloaded by 25 students in one week is displayed in the box plot.  What percent of students download more than 40 iTunes in the week?

• 25%

• 50%

• 75%

• 100%

A population of students in 7th grade consists of 85 girls and 73 boys. A random sample of 20 students is chosen and the gender represented in each sample are shown below. What is the sample proportion of girls in this situation?

Boy, Boy, Girl, Boy, Girl, Girl, Girl, Boy, Girl, Girl, Girl, Boy, Boy, Girl, Girl, Girl, Boy, Girl, Boy, Girl

• 0.4

• 0.5

• 0.6

• 0.7

Answer explanation

12 DIVIDED BY 20

Mary’s middle school has 560 students.  She takes 24 random samples of students and calculates the proportion of students that were on the honor roll all four quarters.  The dot plot represents the sample proportions for Mary’s random samples.  Of the following choices, which is most likely to be the actual proportion of students that were on the honor roll all four quarters?

• 0.2

• 0.4

• 0.6

• 0.7

Answer explanation

0.6 IS THE CENTER OF THE DOT PLOT

The mean number of hours spent on Khan Academy for a sample of 10 seventh grade students is 2.1.  Fa second random sample of 10 seventh grade students have a mean of 2.4 hours for the same month. This is called _______.

A toothpaste ad states they randomly sampled 100 dentists and found “4 out of 5 dentists prefer Crown toothpaste.”  Based on this data, which of the following conclusions are valid?

• Exactly 4 out of 5 dentists prefer Crown toothpaste.

• About 1 out of 5 dentists prefer their patients not use toothpaste.

• About 4 out of 5 dentists prefer Crown toothpaste.

• None of the above are valid.