Plotting probability plot by hand

Click For Summary

Discussion Overview

The discussion revolves around the process of manually plotting a probability plot, specifically in the context of determining if a given dataset follows a normal distribution. Participants explore the steps involved in creating such a plot without the aid of statistical software, focusing on the necessary data transformations and graphical representation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant inquires about the method to plot a probability plot by hand, seeking guidance on the process without using statistical software.
  • Another participant requests clarification and examples to better understand the initial question, noting its generality.
  • A specific example is provided involving a dataset related to the warping of a long metal pipe, with a request for guidance on generating the necessary data for both axes of the plot.
  • The participant mentions familiarity with using Minitab for plotting but expresses a desire to learn the manual method, questioning how to derive the second set of data for the y-axis from a single dataset.
  • There is a reference to using percentiles for calculations, which the participant finds unclear.
  • Another participant suggests that the plot in question is a QQ plot, indicating that observed values should be used for the x-axis and rank-based z-scores for the y-axis.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the method for manually plotting a probability plot, as there are varying levels of understanding and differing approaches suggested.

Contextual Notes

The discussion highlights uncertainties regarding the calculations needed for the axes and the interpretation of percentile usage in the context of probability plots.

Who May Find This Useful

Individuals interested in statistical methods, particularly those looking to understand manual plotting techniques for probability distributions and QQ plots.

level1
Messages
4
Reaction score
0
Anyone knows how to plot a simple probability plot by hand (manually) without using statisical software?
 
Physics news on Phys.org
Can you give an example?
Because now your question is very general, and also very personal (some people will say they can, others won't).
 
Hi,

the example goes something like this:
Assuming a set of data is collected to show warping of a long metal pipe.

0.756 0.856 0.943 0.978 1.12 1.23 1.45 1.67 1.87

Plot a probability plot to ascertain if the data is of normal distribution.

I know how to use minitab to plot the probability plot and then check if it is
more or less a straight line or is there any out-lier.

But I would like to learn how to manually plot a probability plot.
Normally a graph plot will require 2 set of datas, 1 set for the x-axis and the other set for the Y-axis. But now that I have only 1 set of data, how to I use this particular set of data to generate the other set of data for the other axis?

Is there any standard parameters for the x-axis and y-axis?

The textbook says something about using percentile to calculate but I don't really understand what its trying to say... :(
 
I can see you are on the right track. What you are looking for is called qq plot. The way to tell if the data is normally distributed just by plotting their quantiles.
you have observed value as x values. you need rank based z score for the y axis.
http://www.stattucino.com/berrie/graphs.html
 
Last edited by a moderator:

Similar threads

Undergrad Box & Whisker Plot: When, How & Difference
  • · Replies 1 ·
Replies
1
Views
1K
Graduate Probability Density Function: Converting Experimental Observations to PDF
  • · Replies 4 ·
Replies
4
Views
3K
Graduate How to calculate the probability of error in an AWGN channel?
  • · Replies 4 ·
Replies
4
Views
5K
Undergrad T-test: normal probability plot
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad What Software Is Used for Creating Plots in Academic Papers?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Confusion about normal probability plots
  • · Replies 5 ·
Replies
5
Views
2K
Graduate Observing interactions with plots using est. coeff.
  • · Replies 4 ·
Replies
4
Views
2K
Undergrad Understanding the probability density function
  • · Replies 7 ·
Replies
7
Views
3K
How can you modify Python code for effective graph plotting?
  • · Replies 7 ·
Replies
7
Views
3K
High School Weighing Contribution: Scatter Plot Analysis
  • · Replies 7 ·
Replies
7
Views
1K