Can a sample size of 1500 people accurately reflect the opinion of the entire country?

Statistics and Opinion Polls How can a sample of 1500 people accurately reflect entire country? –Gallup Poll example Assumptions –Questions must be free of bias –Random sample –Representative sample –Large sample size/low margin of error

Bias and Polling Questions Please tell me the extent to which you agree or disagree with [this] statement about the definition of marriage… Since gay and lesbian couples already have the same rights as married couples available to them under civil partnership, they should not be allowed to redefine marriage for everyone else.’

Bias? Question should not imply the answer Can be more complicated…

“What do you think is more important – to protect the right of Americans to own guns or to control gun ownership?” Do you see bias in this question? Gun control groups did

Questions free from bias Push polls (example from 2000 SC Primary) –"Would you be more likely or less likely to vote for John McCain for president if you knew he had fathered an illegitimate black child?"

Push Poll example from Texas Callers asked voters "whether they would be more or less likely to vote for Governor Richards if they knew that lesbians dominated on her staff."

More examples… “How likely are you still to Caucus for Bernie Sanders if you knew that he blocked gun control legislation five times as a U.S. Senator?” Bernie Sanders has proposed trillions in new government spending, including $15 trillion dollars more for a government run health care program. Does this make you more or less likely to support him?

Random sample Everyone has the same chance of being selected

-1 in 4 households have only cell service -percentage of cell-only service highest among younger adults, minorities, and groups of the population with high mobility -Federal laws prohibit automated dialing programs to cell phones Can a political opinion survey obtain a random sample WITHOUT including cell phone numbers?

Representative Sample Those who are asked questions must reflect the characteristics of the population

Sample Size Large enough group to answer the questions 1500 responses can get an accuracy rate of +/- 3% ASSUMES: representative and random

Significance of Opinion Polls Media- linkage institution –Tells policy makers what the people want Trustee or delegate? –…do what’s best… (Trustee) –…or do what the public wants… (Delegate) Political Party Leadership –Advancement motivates

Flip flops and whips? Not as important as some scholars think? Flip-flops Party discipline

In small groups, read the article “Nevada: Polling’s Black Hole” Respond to the questions on the back Apply your knowledge