{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

M316 Chapter 10

# Because gallup uses chance to choose its samples the

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ts samples, the laws of probability govern the behavior of the samples. Gallup says that the probability is 95% that an estimate from their sample comes within 3 percentage points of the actual proportion. What does this mean? The Idea of Probability Chance behavior is unpredictable in the short run but has a regular and predictable behavior in the long run. This is the basis of reliance on random samples. If you toss a coin or choose an SRS, the result can't be predicted in advance, but a pattern emerges after many repetitions. Example (10.3) Coin Tossing When we toss a "fair" coin we expect half to be heads and half to be tails. The Count du Buffon (17071788) tossed a coin 4040 times and recorded 2048 heads 2048 for a proportion of = 0.5069 heads. Later (about 1900) Karl Pearson tossed a 4040 12,012 coin 24,000 times and observed 12,012 heads for a proportion of = 0.5005 24,000 heads. As a prisoner of war during WWII, John Kerrich tossed a coin 10,000 times 5067 and got 5067 heads for a proportion of = 0.5067 heads. 10,000 1 M316 Chapter 10 Dr. Berg Here is a plot showing...
View Full Document

{[ snackBarMessage ]}