7.2.3 - Proportion 'In between'

MinitabExpress  – Proportion Between Two z Values

Question: What proportion of the standard normal distribution is between a z score of 0 and a z score of 1.75?

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 Middle
  5. For X value 1 enter 0 and for X value 2 enter 1.75

    This should result in the following output:

    Standard normal distribution from Minitab Express showing that the area between 0 and 1.75 is 0.459941

    The proportion of the z distribution that is between 0 and 1.75 is 0.459941

    Video Walkthrough

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

    MinitabExpress  – Proportion Between Values on a Normal Distirbution

    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 between 60 mph and 73 mph?

    Let's construct a normal distribution with a mean of 65 and standard deviation of 5 to find the area between 60 and 73.

    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
    4. For Mean enter 65
    5. For Standard deviation enter 5
    6. Select A specified X value
    7. Select Middle
    8. For X value 1 enter 60 and for X value 2 enter 73

      This should result in the following output:

      Distribution Plot - Normal, Mean=65, StDev=5; In Between

      On a normal distribution with a mean of 65 and standard deviation of 5, the proportion between 60 and 73 is 0.786545

      In other words, 78.6545% of vehicles will be going between 60 mph and 73 mph. 

      Video Walkthrough

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