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Explore the concept of probability histograms and the normal approximation using probability histograms. Learn how to calculate the probability of specific outcomes and the probability of getting a sum within a range.
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Ch.18 Normal approximation using probability histograms • Review measures of center and spread • For a “large” number of draws, a histogram of observed sums is like a normal curve.
A probability histogram represents chance by area. • The value in the middle of the base of the rectangle represents the sum. • The area of the rectangle equals the chance of getting that particular sum.
Example 1: Coin toss 4 times and count the number of heads. • Draw a box model • List the possible outcomes • Draw a probability histogram • What is the probability of getting exactly 2 heads? • What is the probability of getting 2 or fewer heads?
Activity • Probability Histogram • Empirical Histogram
If the total number of repetitions is large, the histogram for the observed sums (data) is approximately the probability histogram (theory). (Law of averages) • If the number of draws is large (drawing with replacement), the probability histogram for the sum of the draws is approximately the normal curve. (Central limit theorem)
Example 2: What is the chance of getting exactly 50 heads in 100 coin tosses? • Example 3: Using the setting from the probability histogram activity, what is the chance of getting a sum of 3 in 2 draws? What is the chance of getting a sum less than or equal to 3 in 2 draws?