Samples and Population Inference

Everyone of the population has an equal chance of being selected.

• picky sample

• random sample

• friends only sample

• alternating sample

Group A and Group B were randomly sampled from the same population. Which statements below are true? Select all that apply.

• Group A has a greater median than Group B

• Group A has a greater range than Group B

• Group A has greater variability than Group B

• Group B has a greater median than Group A

• You cannot tell which group has the greater median based on the picture.

Keyli gathers the heights of a random sample of six graders and seventh graders and displays the data in box plots. What can she say about the data sets?

• The 6th grade sample has greater variability.

• The 7th grade sample has greater variability.

• The 6th grade sample has the greater median.

• The ranges are equal for both samples.

Mr. Jackson had students grow the same type of plant in two different rooms to test the growing conditions. The results are shown in the box plant. Choose ALL accurate statements below.

• Room 7G has the tallest plant.

• 75% of 7D plants are 8 in. or taller.

• 7G has a greater median height.

• Room 7D has the shortest and tallest plants.

Kerron gathers the heights of a random sample of 6th graders and 7th graders and displays the data in box plots. Which statement below is true?

• The median of the 7th grade sample is greater than the 6th grade sample.

• The 7th grade sample has greater variability.

• The ranges of both data samples are equivalent.

• The median of the 6th grade sample is greater than the 7th grade sample.

Mykel surveyed 15 7th graders and 15 8th graders at his school to see how many hours they spend per day listening to music. He made two box plots to compare the data sets. What inference can he draw from the data sets?

• The range is greater for the 8th graders, so there is greater variability for the 8th graders than the 7th graders.

• The person who listens to music the least is a 7th grader.

• The median is greater for the 7th graders, so they generally spend more time listening to music than 8th graders.

• No inferences can be made from the box plots.

A researcher asked five of his doctor friends if they thought the new Brand X medicine that he developed was effective. Four responded "yes." The researcher used the results to write a TV advertisement claiming that "4 out of 5 doctors prefer Brand X medicine." Is this a valid inference? Explain.

• No, because the doctors asked are not a representative sample of the population of doctors.

• No, because 4 doctors said yes out of 9 who were asked.

• Yes, because the doctors asked are a representative sample of the population of doctors.

• Yes, because 4 doctors said yes out of the 5 who were asked.

Maria collects data from a random sample of 7th graders in her school and finds that 16 out of 20 7th graders participate in after-school activities. How many students should Maria expect to participate in after-school activities if 240 total 7th graders attend Maria's school? Write the numerical answer only.

A movie theater randomly samples the types of admission tickets sold on Friday in the afternoon and the evening. If 400 tickets are sold on a Friday afternoon, use your inference and proportional reasoning skills to determine how many of those 400 tickets would be adult tickets. Type your numerical answer only.

A representative sample of 80 customers in a clothing store was surveyed about how they paid for their purchases. The table shows the responses. Based on the results, which of the following are valid inferences. Select all that apply.

• Tomorrow, 8 out of the first 80 customers will for sure pay with a gift card.

• In a group of 40 customers, it is expected that about 10 will pay with cash.

• About 0.3, or 30%, of all the store's customers will pay with a credit card.

• A sample of 100 customers would provide less reliable data.