3.22 The death penalty. In October 2011, the Gallup Poll asked a sample of 1005

Question

3.22 The death penalty. In October 2011, the Gallup Poll asked a sample of 1005 adults, “Are you in favor of the death penalty for a person convicted of murder?” The proportion who said they were in favor was 61%. How many of the 1005 people interviewed said they were in favor of the death penalty for a person convicted of murder? Gallup says that the margin of error for this poll is ±4 percentage points. Explain to someone who knows no statistics what “margin of error ±4 percentage points” means.

Explanation / Answer

The sample size of Gallup poll i.e n = 1005

Proportion in favor of death penalty for a person convicted for murder i.e. p = 61%

Number of adults in favor of the death penalty for a person convicted of murder = np = 1005*0.61 = 613 adults

Margin of error : Gallup poll is based on information collected from a sample of adults, not the entire population and a certain amount of error is bound to occur ie. the sampling error, which is the error that occurs simply because the researchers aren’t asking everyone. The margin of error is supposed to measure the maximum amount by which the sample results are expected to differ from those of the actual population.

margin of error ±4 % means that we are pretty confident that between 57% (= 61% – 4%) and 65% (= 61% + 4%) of the population will be in favor of the death penalty for a person convicted of murder.

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