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Tag Archives: Normal Distribution
A normal bell curve made with humans
A group of students are stacked according to their heights. The result resembles a normal bell curve. Who are the students in the picture? The image is from the statistics and actuarial science department of Simon Fraser University. These students … Continue reading
Rolling Dice to Buy Gas
The price of gas you pay at the pump is influenced by many factors. One such factor is the price of crude oil in the international petroleum market, which can be highly dependent on global macroeconomic conditions. Why don’t we … Continue reading
The Middle 80% Is Not 80th Percentile
A student sent me an email about a practice problem involving finding the middle 80% of a normal distribution. The student was confusing the middle 80% of a bell curve with the 80th percentile. The student then tried to answer … Continue reading
Comparing Growth Charts
Suppose both an 8year old boy and a 10year old boy are 54 inches tall (four feet six inches). Physically they are of the same heights. But a better way to compare is to find out where each boy stands … Continue reading
An Example of a Normal Curve
One way to estimate probabilities is to use empirical data. However, if the histogram of the data shapes like a bell curve (or reasonably close to a bell curve), we can use a normal curve to estimate probabilities. All we … Continue reading
Interpreting ACT Scores
The ACT is a standardized test that is used for college and university admissions in the United States. According to their web site, the ACT test “assesses high school students’ general educational development and their ability to complete collegelevel work”. … Continue reading
The Safest Driving City in America
Which city in America has the worst drivers? When I asked this questions, many people guessed New York or Los Angeles. How about the city with the safest drivers? According to a recent report released by The Allstate Insurance Company, … Continue reading
A Student’s View of the Normal Distribution
In my teaching, I always strive to encourage students to look at statistics from a practical point of view. In a recent class period covering the normal distribution, I indicated that data values more than 3 standard deviations away from … Continue reading →