# TOEFL Q4: Sampling Bias

### In this lesson, your tutor will help you go over question four from the TOEFL speaking test. Read the text below out loud with the tutor.

Sampling Bias

Statistical surveys are an important way of gathering information about large groups of people. However, some surveys do not include all of the members of a group. When this happens, it is called sampling bias. Sampling bias often occurs because a small number of survey methods are used. The main problem of sampling bias is that it often produces results that are incorrect.

### Listen to a short lecture related to the reading. Note to tutor: read the text to the student. The text is not presented to the student in the actual test.

Now I want to tell you how sampling bias led to one embarrassing news story about the 1948 presidential election. On the night of the election, one newspaper wrote on its front page that Thomas Dewey was defeated President Truman in the election. The newspaper wrote this story before the votes were counted. How did the newspaper come up with this headline? It conducted a survey. The problem with the survey was that it was only done over the telephone. Back then, only rich people had telephones. And rich people were mo likely to vote for Due. But most people wanted to vote for Truman. Since they did not have telephones, they were not included in the survey. Because of this, the survey was completely wrong. President Truman won the election over Dewey by a huge margin.

Question

The professor explains sampling bias by giving one example. Explain the example and how it explains the concept of sampling bias.

Preparation time: 30 seconds l Response time: 60 seconds

### Use the chart below to explain the main idea and the key points of the lecture.

Guideline
 Topic The main idea of the lecture is the __ Detail 1 The professor explains that one newspaper incorrectly wrote that Dewey __ in the election. The newspaper wrote this story based on a __. Detail 2 The survey was done __, so it only included rich people. These people were more likely to __. Therefore, the survey results were __.

### Give a brief spoken response to the questions based on the announcement and the conversation.

1. What is the main problem with sampling bias?
•   The main problem with sampling bias is that it produces __.
2. What was the survey method talked about in the lecture?
• The survey method talked about in the lecture was __.
3. How did this survey method affect the results of the survey?
• This method affected the results by including only __.