Answer Happy

The left atrium is one of your heart's four chambers-it is where your heart receives freshly oxygenated blood from your lungs. Its size is directly related to your body size and it may change with age; additionally, the size of the left atrium is one measure of cardiovascular health. When the left atrium is enlarged, there is an increased risk of heart problems. A group of researchers studied the hearts of over 900 children ages 5 to 15 years, and they concluded that for healthy children, left atrial diameter can be modeled by a normal distribution with a mean of 26.2 mm and a standard deviation of 4.1 mm. Normal distributions are continuous probability distributions that are symmetric, bell shaped, have a total area under the curve equal to 1, and are sometimes referred to as a normal curve. When a normal distribution is a reasonable model for a random variable, areas under the normal curve can approximate various probabilities related to that variable. There are infinitely many unique normal distributions, differentiated from one another with a mean, μ, and standard deviation, o, but they can all be converted to the standard normal distribution whose mean is 0 and standard deviation is 1 to simplify probability calculations and facilitate comparisons between variables. In working with normal distributions, you need the following general skills: 1. Use the normal distribution to calculate probabilities, which are areas under a normal curve. 2. Characterize extreme values in the distribution, which might include the smallest 5%, the largest 1%, or the most extreme 5% (which consists of the smallest 2.5% and the largest 2.5%). We will learn how to use these general skills in SALT. The normal distribution that models the size of the left atrium (in mm) in healthy children ages 5 to 15 has a mean μ = mm and standard deviation o = mm.