Random Sampling and Reasoning with Mean

Yadira wanted to estimate the mean number of words per page in a 180-page book she is reading. Which if these sampling methods gives the best estimate of the mean word count per page in the book?

• Count the words on one randomly chosen page.

• Calculate the mean word count for a sample consisting of the pages with pictures.

• Calculate the mean word count for a sample of 20 pages selected by choosing every 9th page.

• Calculate the mean word count for a sample consisting of the 10 pages that appear to have the most words.

Using your inference skills and proportional reasoning, predict the number of purple jellybeans in a bag of 200 total jellybeans if a random sample of 25 resulted in 4 purple jellybeans. I predict there will be _________ purple jellybeans.

Johanna was running for class president. She wanted to know if she had a good chance of winning the election, so she decided to have her classmates help her with surveys. Michael surveyed a random sample of 10 students from the school. 7 of them said they would vote for Johanna. If there are 230 students in the school, and all of them vote, what is Michael’s best estimate of the number of students who would vote for Johanna? _________ students

Which statement best describes a random sample of all students in a middle school?

• Of all the students who are on the track team, the first three to finish a race are selected.

• Of all the students who are in the drama club, every third student on the roster is selected.

• Of all the students who complete an assignment, the first, third, and tenth students are selected.

• Of all the students who attend a school-wide assembly, those sitting in every third seat are selected.

Use the table to find the mean

• 105

• 111

• 118

• 130

Ana wants to know the average student’s opinion of the tardy policy at her school. Which group of students should she survey in order to achieve the most accurate results?

• 30 of her friends

• 30 randomly selected students in the school

• 30 students who are often tardy

• 30 students who are often on time

An inspector tests 15 random samples of 100 microchips from Hitech Microchips and 15 random samples of 100 microchips from Speedy Microchips. The dot plots show the number of defective microchips in each sample. What is the mean for both Hitech Microchips and Speedy Microchips?

• HM: 5.8

  SM: 6.4

• HM: 5.6

  SM: 6.6

• HM: 5.8

  SM: 6.6

• HM: 6.0

  SM: 6.2

Marcus has three random samples of the same size from a population of 700 people. In one sample, 53% of people have a library card. In another, 51% of people have a library card. In the third, 43% have a library card. Based on the mean of the three samples, how many people with a library card should he expect are in the population?

• 301

• 357

• 371

• 343