7.2.2 - Proportion 'Greater Than'
MinitabExpress – Proportion Greater Than a z Value
Question: What proportion of the standard normal distribution is greater than a z score of 2?
Recall that the standard normal distribution (i.e., distribution) has a mean of 0 and standard deviation of 1. This is the default normal distribution in Minitab Express.
- On a PC: from the menu select STATISTICS > Distribution Plot
On a Mac: from the menu select Statistics > Probability Distributions > Distribution Plot - Select Display Probability (Note: The default is the standard normal distribution)
- Select A specified X value
- Select Right tail
- For X value enter 2
This should result in the following output:
The area of the z distribution that is greater than 2 is 0.0227501
Select your operating system below to see a step-by-step guide for this example.
MinitabExpress – Proportion Greater Than a Value on a Normal Distribution
Question: Vehicle speeds at a highway location have a normal distribution with a mean of 65 mph and a standard deviation of 5 mph. What is the probability that a randomly selected vehicle will be going more than 73 mph?
Let's construct a normal distribution with a mean of 65 and standard deviation of 5 to find the area greater than 73.
To calculate a probability for values greater than a given value in Minitab Express:
- On a PC: from the menu select STATISTICS > Distribution Plot
On a Mac: from the menu select Statistics > Probability Distributions > Distribution Plot - Select Display Probability
- For Distribution select Normal (Note: This is the default)
- For Mean enter 65
- For Standard deviation enter 5
- Select A specified X value
- Select Right tail
- For X value enter 73
This should result in the following output:
On a normal distribution with a mean of 65 and standard deviation of 5, the proportion greater than 73 is 0.0547993
In other words, 5.47993% of vehicles will be going more than 73 mph.
Select your operating system below to see a step-by-step guide for this example.