Lesson 12

More about Sampling Variability

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Problem 1

One thousand baseball fans were asked how far they would be willing to travel to watch a professional baseball game. From this population, 100 different samples of size 40 were selected. Here is a dot plot showing the mean of each sample.

A dot plot for “sample mean distance in miles.” The numbers 40 through 84, in increments of 2, are indicated

Based on the distribution of sample means, what do you think is a reasonable estimate for the mean of the population?

Solution

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Problem 2

Last night, everyone at the school music concert wrote their age on a slip of paper and placed it in a box. Today, each of the students in a math class selected a random sample of size 10 from the box of papers. Here is a dot plot showing their sample means, rounded to the nearest year.

A dot plot for “sample mean age.” The numbers 31 through 42 are indicated. 
  1. Does the number of dots on the dot plot tell you how many people were at the concert or how many students are in the math class?
  2. The mean age for the population was 35 years. If Elena picks a new sample of size 10 from this population, should she expect her sample mean to be within 1 year of the population mean? Explain your reasoning.

  3. What could Elena do to select a random sample that is more likely to have a sample mean within 1 year of the population mean?

Solution

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Problem 3

Andre would like to estimate the mean number of books the students at his school read over the summer break. He has a list of the names of all the students at the school, but he doesn’t have time to ask every student how many books they read.

What should Andre do to estimate the mean number of books?

Solution

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(From Unit 8, Lesson 11.)