Using a Sample to Make Predictions

Think About the Process There were about people living in Lougheedville. Samy wanted a new swimming pool to be build. He decided to find out how many people agreed with him.

Think About the Process Instead of asking each person, Samy decided to ask a sample of people. He planned to use their answers to predict how many people in Lougheedville wanted a new pool.

Think About the Process Samy first had to decide on the number of people to ask. This number is called the sample size. Samy decided to ask 100 people. When choosing the people to ask, Samy had to be sure that his sample was not distorted or biased.

Time Out! What is a sample and what is bias? Something for your notes! tml tml

Think About the Process Suppose Samy’s sample was not biased, and he found that 60 people out of 100 said they were in favour of a new pool. This means that 60/100 or 60% of the sample wanted the pool. Samy applied the percent from the sample to the whole population of Lougheedville. 60% of = 0.6 x =

How many people agreed with Samy? From his sample, Samy predicted that, if he had asked everyone in Lougheedville, would have wanted a new pool.

Problems and Applications 1. There were 500 students at Gagan’s school. Gagan was asked to find out how many could swim. Gagan surveyed 50 students. He found that 35 students in his sample could swim. How many of the 500 students would Gagan predict could swim? Work through this question. Show your work. When you think you have the answer raise your hand.

Problems and Applications: The Answer This means that 35/50 or 70% of the sample wanted the pool. You must then apply the percent from the sample to the whole population. 70% of 500= 0.7 x 500 = 350

Now you try! Work on page 307 of Math Power 7