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.

Steps
  1. On a PC: from the menu select STATISTICS > Distribution Plot
    On a Mac: from the menu select Statistics > Probability Distributions > Distribution Plot
  2. Select Display Probability (Note: The default is the standard normal distribution)
  3. Select A specified X value
  4. Select Right tail
  5. For X value enter 2

This should result in the following output:

Minitab Express output: z distribution showing the area above 2

The area of the z distribution that is greater than 2 is 0.0227501

Video Walkthrough

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:

Steps
  1. On a PC: from the menu select STATISTICS > Distribution Plot
    On a Mac: from the menu select Statistics > Probability Distributions > Distribution Plot
  2. Select Display Probability 
  3. For Distribution select Normal (Note: This is the default)
  4. For Mean enter 65
  5. For Standard deviation enter 5
  6. Select A specified X value
  7. Select Right tail
  8. For X value enter 73

This should result in the following output:

Distribution Plot - Normal, Mean=65, StDev=5; Greater Than

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.

Video Walkthrough

Select your operating system below to see a step-by-step guide for this example.