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Jan 21, 2021 · There are many programs available that will calculate the probability for a normal curve including Excel and the TI-83/84. There are also online sites available. The following examples show how to do the calculation on the TI-83/84 and with R.
To calculate probabilities associated with normal random variables in Excel, use the norm.dist (x,μ μ,σ σ,logic operator) function. For x, enter the value for x. For μ μ, enter the mean of the normal distribution. For σ σ, enter the standard deviation of the normal distribution.
- Example 1: Normal Probability Greater Than X
- Example 2: Normal Probability Less Than X
- Example 3: Normal Probability Between Two Values
- Example 4: Normal Probability Outside of Two Values
Question: For a normal distribution with mean = 40 and standard deviation = 6, find the probability that a value is greater than 45. Answer: Use the function normalcdf(x, 10000, μ, σ): normalcdf(45, 10000, 40, 6) = 0.2023 Note: Since the function requires an upper_x value, we just use 10000.
Question: For a normal distribution with mean = 100 and standard deviation = 11.3, find the probability that a value is less than 98. Answer: Use the function normalcdf(-10000, x, μ, σ): normalcdf(-10000, 98, 100, 11.3) = 0.4298 Note: Since the function requires a lower_x value, we just use -10000.
Question: For a normal distribution with mean = 50 and standard deviation = 4, find the probability that a value is between 48 and 52. Answer: Use the function normalcdf(smaller_x, larger_x, μ, σ) normalcdf(48, 52, 50, 4) = 0.3829
Question: For a normal distribution with mean = 22 and standard deviation = 4, find the probability that a value is less than 20 or greater than 24 Answer: Use the function normalcdf(-10000, smaller_x, μ, σ) + normalcdf(larger_x, 10000, μ, σ) normalcdf(-10000, 20, 22, 4) + normalcdf(24, 10000, 22, 4) = 0.6171
Oct 21, 2024 · However, not all areas of the curve are as simple to calculate as the two halves. When finding the areas and their corresponding probabilities under the curve, this three step process is useful: 1. Sketch, 2. Shade, and 3. Solve. Start by sketching the normal curve to provide a visual representation of the problem.
This normal distribution calculator (also a bell curve calculator) calculates the area under a bell curve and establishes the probability of a value being higher or lower than any arbitrary value X. You can also use this probability distribution calculator to find the probability that your variable is in any arbitrary range, X to X₂, just by ...
Nov 5, 2020 · To find the corresponding area under the curve (probability) for a z score: Go down to the row with the first two digits of your z score. Go across to the column with the same third digit as your z score. Find the value at the intersection of the row and column from the previous steps.
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Aug 12, 2022 · Identify the characteristics of a normal distribution. Identify and use the Empirical Rule (68-95-99.7 Rule) for normal distributions. Calculate a z-score and relate it to probability. Determine if a data set corresponds to a normal distribution.
